Class Size


Class size refers to the number of students in a given course or classroom, specifically either (1) the number of students being taught by individual teachers in a course or classroom or (2) the average number of students being taught by teachers in a school, district, or education system. The term may also extend to the number of students participating in learning experiences that may not take place in a traditional classroom setting, or it may also refer to the total number of students in a particular grade level or “class” in a school (although this usage is less common in public education).

It should be noted that schools, districts, and state and federal education agencies commonly track and report “average class sizes.” While average class sizes are commonly expressed as a ratio of students to teachers, a “student-teacher ratio” is usually different than average class size. For a more detailed discussion, see student-teacher ratio.


In recent decades, a variety of reform efforts have been focused on decreasing class sizes, or the average class sizes in an education system, as a strategy for improving school and student performance. After research studies found that smaller class sizes could have positive effects on student learning and academic achievement, many initiatives—both at the level of state and federal policy, and in individual schools and districts—sought to lower student-teacher ratios. The basic rationale is that if teachers have fewer students, they can devote more time and attention to each student, including more time diagnosing specific learning needs, critiquing work products, and giving students one-on-one instruction and academic support, for example.

To understand how class size can affect teaching, consider the following hypothetical example. If a teacher has five classes with 20 students in each class, the teacher is responsible for 100 students. If each class is increased to 30 students, the teacher would then be responsible for 150 students—a 50 percent increase in the teaching workload. If a teacher with 20 students in each class spends only 15 minutes reading, analyzing, and responding to a writing assignment (a short amount of time), the teacher will have to devote 300 minutes to the process for each class—or about five hours—while five classes given writing assignments would require 25 hours. For a teacher with 150 students, the time required would be 2,250 minutes—or nearly a full 40-hour workweek. So if the teacher gave one writing assignment a week in each class, the time required to teach the course and score the writing assignments would likely be between 65 and 80 hours, depending on class sizes. As this example illustrates, at a certain point class size, for purely logistical reasons, will affect the instructional options available to teachers, since the demands of lesson preparation, teaching duties, and assignment grading can quickly become unmanageable as class sizes increase. And the more students that teachers have, the more likely it is that they will have to rely on instructional methods that require less time to complete, such as grading short-answer worksheets or scoring multiple-choice tests, for example.

While average class sizes may be reduced in a variety of ways, the two main approaches have been through educational policy and funding mechanisms, and by reconfiguring the organizational and instructional systems in a school.

Both the federal government and numerous states have passed legislation and adopted supplemental funding measures intended to either require or encourage schools to reduce average class sizes. Because reducing student-teacher ratios generally requires the hiring of additional teachers, possibly even a significant number of teachers (in the case of states and large school districts), some class-size-reduction policies can entail significant increases in educational expenditures—particularly when schools look to hire experienced and qualified teachers (who generally cost more) or teachers in subject areas with a shortage of qualified candidates.

Since the desired benefits of smaller class sizes do not necessarily require lower student-teacher ratios, an alternative way to reduce, or effectively reduce, class size is to use a variety of instructional- and school-configuration strategies broadly known as “small learning communities.” While many different school designs and teaching methods are used to create small learning communities within new or existing schools, the general goal is to increase the amount of one-on-one attention, personalized instruction, or academic support for students. In small learning communities, students are paired with teachers, counselors, and support specialists who, over time, get to know the students and their specific learning needs well, enabling them to educate the students more effectively. Even though the average student-teacher ratio in a school may or may not change in small-learning-community settings, students will be grouped and supported in ways that can potentially reproduce the benefits of smaller class sizes. It is important to note, however, that smaller learning communities, and related strategies such as advisories or teaming, may take a wide variety of configurations from school to school, and they may be more effective or less effective depending on the quality of their design and execution.


In recent decades, there has been much debate about class size and whether simply reducing student-teacher ratios will lead to improved student learning and academic achievement—particularly on a large scale, such as in a state’s public-education system. While reducing class sizes, and the attendant professional burdens placed on teachers, seems to be a logical way to improve the amount of instructional time and attention given to each student, research studies have found mixed results: some indicate that smaller class sizes produce educational benefits for students, but others suggest that strong teaching is the main factor, and that simply hiring more teachers—who may not necessarily more experienced and skilled teachers—will simply increase educational costs without producing the desired results.

In the ongoing debate about class size, costs tend to play a significant role. For example, critics of lower student-teacher ratios may argue that an effective teacher can teach a larger class of students better than an ineffective teacher can teach a smaller class, and therefore the benefits do not justify the increased costs. Proponents may counter that both effective and less-effective teachers will be more effective in smaller classes, and that such across-the-board benefits for all students justify the additional costs. Of course, many other nuanced arguments are also made on both sides of the debate.

The class-size debate also entails several technical arguments. For example, there is ongoing debate over the precise point at which students begin to benefit from smaller classes. Some evidence suggests that lowering class sizes may not have a positive affect on student achievement until the average size drops below 20 students, and that educational benefits are measureable only when student-teacher ratios fall to 18 to 1 or 15 to 1. In this case, a state might expend a significant amount of time, human resources, and money on reducing average class sizes, for example, but then fail to reduce ratios enough to see any measurable benefits.

Another common source of discussion and debate is the most optimal class size for students of different ages or grade levels. For example, younger students typically require more time, attention, and instructional support from teachers, and some studies have have a correlation between smaller class sizes at the elementary level and better academic results, particularly for high-need student populations and when smaller class sizes are maintained across grade levels (e.g., kindergarten through third grade). For this reason, some educators and experts argue that class size is a more important instructional factor when students are younger, and that the benefits of small class sizes diminish as students age and progress in their education.

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