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The Right Size for Learning:
Class Sizes in Massachusetts

By Colin A. Jones, April 27, 2015
The Right Size for Learning

For all endnotes please see the pdf version of this paper.


All young people deserve to learn in supportive classrooms that enhance their full academic, social, and personal development. Smaller class sizes are one way to help teachers provide supports tailored to each student’s individual needs. In fact, many effective educational programs – high quality preschool, effective summer learning programs, and the Commonwealth’s hands-on vocational schools – rely on using smaller classes.

It is important to note, however, that class size reduction efforts have not always been well implemented. There have been both prominent successes and costly initiatives that did not achieve positive results as intended.

The aims of class size reductions are straightforward. First, reducing class sizes can allow more individualized support and attention to students. Second, smaller class sizes can make classrooms more manageable for teachers leading to more time on task and fewer disruptions.

This report explores the connection between class size and student learning, distills key principles to inform policy debates, compares current class sizes in Massachusetts with optimum sizes identified by leading research, and provides estimates for what it would cost to bring class sizes down to these levels in targeted districts.

Evidence from Class Size Reduction Efforts Across the Country

Research on the relationship between class size and student success has identified several key insights.  These can be distilled to four main principles:

  1. Target the early grades. Class size reductions have been most effective with early elementary classes, lowering class sizes for students in kindergarten through 3rd grade. In particular, children in kindergarten and 1st grade classes have benefited the most from smaller class sizes. This is in part because more individual attention from teachers can be most beneficial for students during the critical early elementary years where basic academic concepts, social skills, and school behavior are formed.
  2. Target students with the greatest need. While all students can benefit from smaller classes, there is evidence that students of color and low-income students particularly benefit from well-designed class size reductions. In some cases these students have experienced much greater positive impact.
  3. Ensure that classes are staffed with strong teachers. Reducing class sizes often involves hiring additional teachers, and it is critical to ensure these new teachers are highly qualified. When California implemented a statewide class size reduction plan, they did not get the intended results, in part because they staffed up with under-qualified teachers. Rushed implementation in California also led districts to use inferior facilities as new classrooms.
  4. Combine class size reductions with other effective school practices. Class size reductions are most effective when they are part of larger school reform efforts, combining them with other effective practices. These practices include appropriate teacher training and support, increased learning time that provides additional enrichment and academic opportunities, and services that address the non-academic social barriers that students face outside of the classroom.

Case Studies on Class Size Reduction

1) Tennessee Project STAR – A Well-Designed Small Class Size Program

Perhaps the best studied class size reduction program is the Student Teacher Achievement Ratio project (Project STAR) undertaken in the 1980s in Tennessee. Project STAR supported small class sizes for early elementary students (kindergarten to 3rd grade) over four years. Research on this effort has consistently found positive academic improvement for kids whose classes were reduced to roughly 15 students. Kids in these smaller classes continued to do better throughout the later grades and also did better on college entrance exams. The positive impacts were greatest for low-income students, students of color, and those in urban schools.

Project STAR was designed and implemented in a way that allowed researchers to clearly identify the impact of smaller class sizes. Project STAR had a fairly representative mix of students across Tennessee including roughly 12,000 kids in more than 40 school districts in inner-city, suburban, and rural areas.  Since it was a demonstration study, it received significant state investment, $12 million ($27 million in current dollars) but did not go in effect across all of Tennessee.  The STAR program allowed the most rigorous evaluation because it randomly assigned teachers and students to either large classes with 22 to 26 students or small classes with 13-17 students.  This ensured that any differences in academic performance could be attributed to smaller classes.

STAR students randomly assigned to small classrooms gained the equivalent of roughly 2-3 months of learning in reading and math.  The gains from small classes in Project STAR for students of color was twice the overall average in kindergarten and 1st grade, roughly equal to five months of additional academic growth.  However, the additional gains for African-American kids were similar to others by 2nd and 3rd grade. The benefits of small classes in STAR were greater for low-income, African-American, and inner-city students, and these additional benefits were present for each of these groups independently when controlling for the other variables.

Additionally, this immediate boost from small classes lasted over time. A five year follow-up study found that having been in Project STAR small classes had a similar effect five years later as it did when students were directly participating in smaller classes.  Gains in reading, math, and science persisted through 8th grade.  Benefits were also greatest for students who had been in small classes for more years during kindergarten through 3rd grade.


The positive long-term impact of Project STAR also improved college preparation. The share of high school seniors taking college entrance exams was 10 percent greater for those who were in smaller classes a decade earlier. ACT scores were also higher for these students, particularly African-Americans.  

2) California’s Class Size Reductions – A Cautionary Tale

Attempting to build on the success of Project STAR in Tennessee, the state of California in the 1990s implemented a large-scale statewide class size reduction plan to boost achievement for early elementary students. Instead of replicating the effective program features in Tennessee, however, the California initiative was staffed by lower quality teachers, was poorly targeted, and didn’t significantly reduce class sizes. It ultimately failed to deliver the same results.

California’s class size reduction program was at significantly greater scale than Project STAR. The state allocated up to $1.5 billion annually from 1996 to 2002 to reduce class sizes.  The level of funding, which made it one of the largest education reforms in the state’s history, reflected the goal of making small classes the norm across California. This was in contrast to starting with a small to medium scale demonstration study as happened with the $26 million dollar program in Tennessee.

The California class size reduction program failed to deliver results for a few key reasons, including:

  • The class size reductions resulted in lower quality teachers and facilities. The class size program created a need to hire 29,000 teachers in four years.  This led to a large increase in under-qualified teachers. The share of kindergarten to 3rd grade teachers who were not fully credentialed increased by a factor of seven (from 1.8% to 12.5%).  When the initiative was fully implemented, one in five teachers in schools with large populations of low-income students was under-qualified.  The plan also created a need for 18,000 new classrooms. This led to use of inadequate makeshift facilities, such as libraries and auditorium stages, and the repurposing of space away from other services such as special education, arts, and after-school.
  • Class sizes were not reduced enough to make a difference for participating schools. California gave flat grants of slightly over $1,000 per-student (2015 dollars) once districts reached the goal of class sizes of 20 or fewer.  This approach failed to provide the support to achieve the significantly smaller class sizes attained by students in Tennessee. California’s definition of small classes as 20 or fewer students was only 2 students below the range for large classes in the Tennessee study, which featured reduced class sizes 33 percent smaller.
  • The initiative was not targeted to support the students most in need. Given that districts received funding only after reaching the smaller class size benchmark, the program more rapidly benefited relatively affluent cities and towns that could already afford lower class sizes.  Lower income districts, the most in need of additional funding and support lagged behind on implementing smaller classes.   Districts serving more low-income and immigrant youth faced the most overcrowded classrooms, lacked adequate facilities to reduce classes, and struggled to find additional teachers who were certified to serve English learners.  On average, districts with more students of color received less class size reduction grant funding.


In the first two years of implementation, California students in these smaller classes realized little measurable achievement gains.  There were no better results from smaller classes for students who were academically behind, English language learners, or low-income students. However, there was a slight benefit of smaller class sizes for African-American students.  

These disappointing results provide a cautionary tale. Class size reductions should be implemented with well prepared and supported teachers. Policymakers should implement these efforts at reasonable scale and over several years, in a way that prioritizes the students most in need of additional support. Smaller class sizes also should be made available along with adequate facilities.

3) Wisconsin Project SAGE – Combining Small Class Sizes with Other Effective Practices

Other small class size initiatives have been more successful. For instance, Wisconsin’s Project SAGE (Student Achievement Guarantee in Education), initiated in 1996, effectively used smaller class sizes to improve the achievement of low-income students. The Wisconsin effort did more than just reduce class sizes. It combined smaller class sizes with effective teacher development and other supportive school practices. Project SAGE much more effectively targeted these services to benefit low-income youth.

A diverse range of districts participated in Project SAGE, including urban areas (such as Green Bay, Madison, and Milwaukee), and 18 smaller districts.  Eligible school districts had to have at least one school with over half low-income students and eligible schools had to have at least 30 percent low-income students.  These districts received up to $2,800 per student to implement smaller classes and total program funding reached $23 million annually ($33 million in current dollars) when it was fully implemented in 1999.  The program was rolled out gradually, starting with kindergarten and 1st graders, then expanding as students progressed to serve 2nd and 3rd graders. Project SAGE reached an average of 3,700 students per-year over the initial five years.

Project SAGE combined smaller early elementary class sizes in low-income schools with several other elements including teacher professional development, rigorous curriculum, and increased learning time and other social supports.  SAGE classrooms had 15 students per teacher, lowering averages by close to ten students, consistent with Tennessee’s Project STAR.  SAGE schools also used curriculum identified by teacher and administrator associations as setting ambitiously high academic standards.  

SAGE schools had strong professional development and collaborative teaching practices. The overwhelming majority of SAGE principals and teachers, 80-90 percent, reported that their schools had implemented collaborative planning between multiple teachers, participated in team teaching, and engaged in formal professional development workshops and conferences.  However, there were also areas of professional development that could have been strengthened, including the fact that only 54 percent of teachers had a formal written development plan, and only 17 percent received specific training on how to take advantage of smaller-class sizes.  

Project SAGE also infused schools with a host of additional enrichment activities, with substantial variation in the specific services offered. The most common were school breakfast, after-school learning such as Girl Scouts and tutoring, and summer reading programs.  There were also several parent focused services including adult literacy programs, family resource centers, and social events that connected families with the school community.

Wisconsin’s SAGE program achieved similar positive results as Project STAR had in Tennessee. In the 3rd year of the program, early elementary students in Project SAGE achieved two to three months of additional academic progress in math, reading, and English versus comparison schools.  African-American students had greater gains, meaning that race-based achievement gaps for African-American students were reduced.  Gains were consistent and did not fade out over time.


Implementation of Project SAGE was paired with extensive teacher surveys in order to help researchers identify how small classes helped improve instruction. Project SAGE allowed for more individualized attention for students, improved classroom management, and provided more hands-on learning opportunities that resulted from more orderly and well-managed classrooms.  Project SAGE educators reported they were better able to learn about the individual strengths and weaknesses of students and pair this knowledge with strategies to meet these needs.  Project SAGE classes had fewer discipline problems and more time to promote positive relationships, which was further enhanced by maintaining small classrooms over several years.  This allowed familiarity with team teaching, collaborative planning, and integration of professional development into practice.

With other positive conditions in place, SAGE teachers implemented more hands on activities and student-centered learning practices that allowed students and teachers to get more in depth with academic content.  Although variation in the increased learning time opportunities and social supports makes overall conclusions difficult, these additional programs, along with the lower class sizes, expanded what was available to kids, while helping to increase family engagement through social events, services, and increased communication.

Costs and Other Considerations for Class Size Reductions

The Commonwealth can adapt the lessons learned from class size efforts around the country. The effective examples of Project STAR in Tennessee and SAGE in Wisconsin suggest that we could boost achievement by reducing class sizes to 15 students in kindergarten through 3rd grade, particularly in low-income schools. Class size reductions should make sure all classes have well-prepared teachers and other supportive services. However, because previous Roadmap to Expanding Opportunity reports have detailed policy options and costs for teacher training, increased learning time, and comprehensive child and family service programs (wraparound services), the following discussion will be limited to targeted class size reductions.

Smaller class size efforts could start by targeting schools that serve high proportions of low-income students most in need of additional support. One way to identify target schools is to select those eligible for school-wide services through federal Title I grants. To reach this threshold, schools must have 40 percent or more low-income students.  In 2013-2014, there were 461 elementary schools that serve 40 percent or more low-income students across Massachusetts.  Among these schools, 414 (90 percent) have class sizes larger than 15, with an average class size just under 20 students.  Details on the target schools and a sample of districts with these focus schools are listed in the tables below.

The 20 students per-class average from recent state data understates typical class sizes. This is because of the way the Department of Elementary and Secondary Education collects this data from schools. The state’s class size averages include mainstream classrooms as well as smaller self-contained classes for special education students and English Language Learners. Combining these separate types of classrooms lowers the average class size compared to what is happening in practice. To illustrate this, consider an elementary school with seven classrooms, one of which is a separate special education class of eight students, the other six of which are mainstream classes with 22 students. The average class size including both types of classes is 20 students, however 94 percent of kids are in a class of 22 students. This data issue suggests that the cost estimates below somewhat understate the actual cost of reducing non-special education and ELL classes down to 15 students.



Each target school has a specific number of additional teachers necessary to reach class sizes of 15. We find that figure by dividing the total number of students at that particular school by 15 and determining how many additional teachers would be needed to reach the optimal class size. Since not all students at these schools are in kindergarten through third grade, the number of teachers necessary is scaled down to match the proportion of students in these selected grades. This calculation leads to an average of between four and five new teachers being added to the 414 target schools, and a statewide total of approximately 1,840 new educators to implement these class size reductions.

To estimate costs of hiring additional educators, we use the most recent teacher salary data from 2012-2013, adjusted to reflect current costs. This uses average salaries from around the state matched to the 414 schools.  Since additional costs for new teachers include both salary and benefits, we add a percentage of salary costs, 18 percent, on top using recent state data on benefits, primarily health insurance.  This may somewhat overstate the salaries and benefits of new teachers, if they are earlier in their careers and start low on district salary scales. However, this accounts for hiring teachers of comparable experience to our current teaching force. Overall, this method suggests that hiring 1,840 K-3 teachers in the affected districts would cost $161 million annually.


Providing more individualized support through smaller class sizes in the early elementary grades is a strategy that has promise for supporting young people in Massachusetts. However, there are numerous factors to account for in making smaller classes a reality. Each community and school district has unique strengths and challenges in bringing this program to their local community. Efforts should incorporate funding for new teacher training and facilities upgrades to create additional classroom space where necessary. Any support from the Commonwealth in funding smaller class sizes should be balanced with the need for participating districts and schools to take ownership of the process. Districts should include smaller class sizes in overall plans including new teacher training, ongoing professional development, student support initiatives, and operational concerns such as school building and facilities plans. If it is done right, creating a foundation of individualized support and attention for children in early elementary school can be part of promoting the academic, social, and personal growth for more kids across Massachusetts.

This research was funded in part by the Annie E. Casey Foundation. We thank them for their support but acknowledge that the findings and conclusions presented in this report are those of MassBudget alone, and do not necessarily reflect the opinions of the Foundation.