How Important Is Class Size?



Class size is one of many factors to consider when choosing or evaluating a school.


How much attention do students at your school get?

Class size is one factor to consider when evaluating a school’s effectiveness. But small class size alone does not ensure a good education. The quality of the teaching, the school leadership, the size of the school, the amount of parent involvement and other factors are important to consider, too.

What’s the difference between class size and student-teacher ratio?

GreatSchools publishes class size information for schools in some states and student-teacher-ratio information in others, depending on what’s available in each state from the respective state Department of Education. It’s important to understand the difference between these two types of data and what they indicate about your school.

When you see class size stats on GreatSchools’ school pages, the number refers to the average class size at the school. Some classes may be larger or smaller than the average number you see. This is especially true in schools which have state-mandated class sizes, particularly in the lower grades. Schools that have mandated lower class sizes in grades kindergarten through 3 may have larger class sizes for the upper grades.

Student-teacher ratios are based on the total number of school instructional staff divided by the total enrollment of students. So this number may include specialist teachers in the arts, literacy specialists, physical education and special education teachers, who may teach smaller groups of students. As a result, student-teacher ratios may show smaller numbers than the actual average class size.

Student-teacher ratios, which in many states are based upon full-time equivalent (FTE) teachers, can appear high for schools that have a large number of part-time teachers. If, for example, a small school has four part-time teachers, who each work 25% of the time, the student-teacher ratio at this school would be calculated based upon one teacher instead of four (because four teachers at 25% is equal to one full-time teacher). This will make the student-teacher ratio appear higher than it really is. If you think your school data shows an exceptionally high student-teacher ratio, check with your school principal to find out why.

What defines a “small class”?

Researchers have found that gains in achievement generally occur when class size is reduced to less than 20 students.

What are the benefits of small classes?

Numerous studies have been done to assess the impact of class size reduction. Although most studies do show a relationship between small class size and increased student achievement, researchers disagree on how to interpret the results. Because there are so many variables in the average classroom — the quality of the teacher, the home environment of the students, the quality of the curriculum, the leadership of the school — it is difficult to draw definitive conclusions about student achievement based on class size alone. In other words, strategies effective in one setting may not be equally effective in another. Nevertheless, studies over a period of years have pointed to a number of trends as a result of lowering class size:

  • Gains associated with small classes generally appear when the class size is reduced to less than 20 students.
  • Gains associated with small classes are stronger for the early grades.
  • Gains are stronger for students who come from groups that are traditionally disadvantaged in education — minorities and immigrants.
  • Gains from class size reduction in the early grades continue for students in the upper grades. Students are less likely to be retained, more likely to stay in school and more likely to earn better grades.
  • Academic gains are not the only benefit of lowering class size. A recent study published in the American Journal of Public Health revealed that reducing class sizes in elementary schools may be more cost-effective than most public health and medical interventions. This is because students in smaller classes are more likely to graduate from high school, and high school graduates earn more and also enjoy significantly better health than high school dropouts.

Why does reducing class size in the early grades have a positive effect?

Education researchers suspect that class size reduction in the early grades helps students achieve because there is a greater opportunity for individual interaction between student and teacher in a small class. Teachers generally have better morale in a small class, too, and are less likely to feel overwhelmed by having a variety of students with different backgrounds and achievement levels. As a result, they are more likely to provide a supportive environment. One researcher, Frederick Mosteller notes “Reducing [the size of classes in the early grades] reduces the distractions in the room and gives the teacher more time to devote to each child.”

In the early grades, students are just beginning to learn about the rules of the classroom, and they are figuring out if they can cope with the expectations of education. If they have more opportunity to interact with their teacher, they are more apt to feel like they can cope.

This theory would also explain why lowering class size in the upper grades may not have the same effect on achievement. Students in the upper grades, who may not have had the benefits of a small class in the early years, have already formed their habits, good and bad, for coping with their classroom environment. Simply reducing the class size at this level may not be enough to change their ways.

The movement to reduce class sizes in public schools

In recent years there has been a movement across the country to reduce class size in public schools. In the late 1990s when state coffers were full, it was politically popular to cut class sizes across the board in the lower grades as a way of pointing dollars toward education in a way that would please voters. Currently, well over half the states have class-size reduction programs for their public schools.

The federal government jumped on the bandwagon in 1998 with a federal class-size reduction initiative. From 1999-2000, the federal government’s $2.6 billion appropriation enabled states and school districts to hire more teachers and reduce class sizes.

Reducing class size is an appealing and visible way for states and public schools to show that they are improving the quality of education. Because smaller classes allow teachers to devote more time to instruction and less to classroom management, smaller classes are popular with teachers unions and administrators. Many studies have shown an increase in student achievement, fewer discipline problems, and improvement in teacher morale and retention as a result of class size reduction. But many researchers question whether the costs outweigh the benefits.

Unintended consequences

In addition to high costs, reducing class size can have unintended consequences. When California reduced class size in 1996, the state found that it did not have enough veteran teachers or classrooms to meet the challenge. Schools were forced to hire new teachers and add portable classrooms to accommodate the state mandate. Schools faced a dilemma: Was it really better to have smaller classes with an inexperienced teacher or larger classes with experienced teachers?

Voters in the state of Florida approved a class-size reduction amendment in 2002 that requires classes to have no more than 18 students in pre-kindergarten through third grade classes, no more than 22 in fourth to eighth grade classes and no more than 25 in high school classes by 2010. The state Board of Education estimates that Florida will need to spend $2 billion to build enough classrooms to meet the demands of the amendment.

Why smaller classes aren’t enough

In California, where class size reduction began in 1996, the research has shown only a modest effect on achievement. This disappointingly small gain has been attributed to the following:

  • Per student funding for class size reduction was not enough to cover the cost for already underfunded districts.
  • School districts had to hire new teachers, many of them not certificated, to meet the needs to make their classes smaller.
  • Serious overcrowding issues forced schools to “cannibalize” other needed facilities — special education rooms, child care centers, art and music rooms, gyms — or rent portable classrooms to accommodate the need for more classrooms.
  • The high cost of implementing class size reduction made it difficult to fund other education needs.

The California experience points to an important lesson. Class size reduction, in and of itself, is not the answer to all the problems in education. In order for a classroom to be effective, it must have a qualified teacher and adequate facilities. When weighing the advantages of class size reduction, schools, districts, and states must consider these questions:

  • Will there be enough resources to provide for high-quality teachers?
  • Will there be adequate facilities to provide for the necessary classrooms?
  • Will putting money into class size reduction take away money from other programs, such as art, music, and child care?

How important is school size?

School size may be as important as class size in influencing student behavior. An April 2000 report by North Carolina’s State Board of Education on the relationship between school size and student achievement and behavior summed up the research in this area nicely. For elementary school students, there’s an inverse relationship between school size and student achievement: smaller elementary schools are associated with higher achievement.

For high school students, the relationship isn’t as straightforward because students at smaller schools don’t necessarily perform better academically; in fact, one study found that students at medium-sized schools (with between 600 and 900 students) did better academically than students from smaller and larger schools. However, research shows that smaller schools are associated with a host of other benefits for high school students: they are less likely to drop out or be expelled; they have better attendance; they’re more likely to be involved in extracurricular activities; and they’re more likely to pursue higher education.


[cp_modal display=”inline” id=”cp_id_bceb2″][/cp_modal]


Other important factors to consider

Teacher workload

In high schools, it is important to consider not only the number of students per class but the nature of the class, and the subject the teacher is teaching. For example, a math teacher might have no problem teaching an advanced math class, or several math classes, with 35-40 students. But an English teacher teaching four classes of 40 students would probably not be able to give the proper attention to written assignments from that many students, and might not give as many assignments because of the large number of students.

Team teaching

Some schools might have classes of 40 taught by a team of two teachers. The class size by itself is not necessarily an indication of the attention students are getting.


Some schools effectively use parents and upper-grade students as volunteers in the classroom. This type of instructional help may not appear in a school’s data about class size.


Share this post