Class size indicates the number of students a classroom teacher is responsible for during the school year. Class size should not be confused with the more commonly used pupil-teacher ratio.

Pupil–teacher ratio is one method used to determine the level of resourcing in education. It is calculated from the number of students in a district compared with the number of EFT (effective full time) educators. The number of educators includes teachers with other responsibilities such as school management, pastoral care special education and counseling. For this reason the pupil – teacher ratio is typically lower than the actual number of students in an average class.

To gain a better overview of educational resourcing, other methods including expenditure per pupil and proportion of GDP devoted to public education should also be consulted.