Average K class size was 23 students this fall and there were three classes (69 students in total in K).
http://www.fcps.edu/it/studentreporting/documents/ElmClassSizeAvg2011.pdf
http://schoolprofiles.fcps.edu/schlprfl/f?p=108:42:4442360063127100::NO:
42_SCHOOL_YEAR,P42_CLUSTER_ID,P42_DIVISION_ID,P42_SCHOOL_ID:201112,1,DIVISION,
It's a fact of life that the class sizes for a school that students from Great Falls, McLean and Vienna attend are going to be bigger than class sizes in less affluent parts of the county. Flip side is that there will be an active PTA.
I don't have kids there, but had kids at a neighboring schools when Colvin Run was built. There was a lot of controversy at the time because parents in Great Falls didn't want their kids attending an elementary school south of Route 7. It's also a bit obnoxious that FCPS makes some kids assigned to Westbriar ES more or less pass by Colvin Run on the bus on their way to Westbriar. But those controversies were a number of years ago and probably forgotten by most.