Sounds like Fayetteville-Manlius, Loudon Valley and North Central were all about the same size (around 1300-1500 in total), though FM also has middle schoolers they can draw from while the others don't.
I can't think of any smaller schools to win. CBA is a boys-only private school that is somewhere around 1k I think (so, comparable enrollment would be about 2k). York, Neuqua Valley and Arcadia are big schools. Gig Harbor and Boerne Champion are bigger than FM/LV/NC (around 1700 for their 4 year total). Coatesville was already mentioned at over 2k, and I think Saratoga Springs is around that size as well.
What about Hilton? They might be about the same size as FM/LV/NC as well.