Pupa hasidic yeshiva in Williamsburg bans 4-section yarmulkes. Students' yarmulkes must have 6 sections and must be completely black. No colored yarmulkes are allowed, and permitted yarmulkes must be soft and big enough to cover the entire head (i.e., cover most of the head an stay on easily).
Related Post: Pupa School Suspends Kids Whose Parents Have Not Promised In Writing To Have Proper Internet Filters And No Smartphones.
[Hat Tip: B.N.]