Studentteacher ratio 
This shows the number of students per fulltime equivalent (FTE) teacher. A low studentteacher ratio is not the same as a small class size. Some schools have teachers who teach specialized subjects with smaller classes. Other schools hire extra teachers to free up class preparation time for their core teaching staff. Both of these possibilities lower the overall studentteacher ratio but not the average class size.
Note that studentteacher ratios based upon FTE teachers can be exceedingly high for schools that have a large number of parttime teachers. If, for example, a small school has four parttime teachers at 25%, the studentteacher ratio at this school would be calculated based upon one teacher instead of four (because four teachers at 25% is equal to one fulltime teacher). This in turn will make the studentteacher ratio appear higher than it really is. If your school has an exceptionally high studentteacher ratio, check with your school principal for an explanation. Source: The school level studentteacher ratio is from the National Center for Education Statistics (NCES) for the 20032004 school year. The state average was calculated by GreatSchools.net using the total number of students enrolled and the total number of FTE teachers provided by NCES for 20032004.
