My school has about 400 students, but it is shrinking. There are 4 sections for 6th grade, 3 for 3rd, 4th and 5th, and I've heard that second grade only has 2. The class size is a bit larger, 27-30, because I think they didn't want to have to pay for another homeroom teacher, so class size got sacrificed instead. However, a giant apartment complex is being built right next to my school, so once that is completed, I expect the school to grow a bit. There is another elementary school almost within sight of my school, but because there are several large apartment complexes in the area, the schools can both keep their classes filled, sort of.
I've heard of schools in my city at are a lot larger and a lot smaller. Some in heavily urban areas have upwards of 2000 kids and some out in the boonies have less than 50. One only has 3 and will likely be shut down due to its size.