NCPA - National Center for Policy Analysis

Student Misbehavior Solves Classroom Size Mystery

August 8, 2002

Some claim that the number of students in a classroom is the most important factor affecting the quality of education. But the empirical evidence is not at all conclusive. In fact, students in countries like Japan produce higher test scores although classes are quite large.

The key to solving the "class-size" puzzle is the public good nature of classroom education. As with other public goods, such as roads, classrooms can suffer congestion. Classroom congestion is caused by student misbehavior. Misbehaving students produce what economists call "a negative externality" borne by the rest of the class.

  • For instance, if students misbehave just 2 percent of the time, that reduces the effectiveness of teaching in a class of 25 students to 60 percent.
  • If the class has 40 students instead of 25, teaching effectiveness drops to 45 percent -- thus classroom size amplifies the effect of individual misbehavior rates.
  • One way to deal with the problem is to reduce classroom size if the misbehavior rate is high, and increase it if it is low.
  • Private schools, however, don't tolerate high rates of misbehavior, and many have higher teacher to student ratios than public schools.

Some attribute public school student misbehavior to the quality of teachers -- claiming that if schools can attract better teachers with higher salaries, for example, the increased cost can be more than offset by larger classroom size and higher educational output. However, private schools tend to pay teachers less than public schools.

The real problem, say some analysts, is that public schools, unlike private ones, are required to educate any student, short of violent criminal misbehavior. Since many public schools do not allow teachers to use effective methods of controlling students -- such as corporal punishment, isolation and ostracism -- there are few ways teachers can maintain discipline.

Source: "The Bad Apple Principle," Economic Intuition, Fall 2001; based on Edward P. Lazear, "Educational Production," Quarterly Journal of Economics, August 2001.


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