Judging from the faculty/staff directory, there are 4 K classes this year. I know that a friend's child has 12 students in his K class this year. We toured the school this year, and their largest class size is 25 kids in 4th grade. They also have some unused classroom space, so they are far from needing portables. I had a child in the school in a preschool program for a year and I was very impressed with my interactions with the principal during that time.
Here's a link to the faculty/staff directory:
http://www.montgomeryschoolsmd.org/schools/glenhavenes/parentresources.aspx?id=443952