Public schools are government institutions. These institutions prevent individuals from engaging openly in the practice of their own religions via simple prayer. These same institutions prevent children from pointing their fingers in pretend gunplay. These institutions hold routine lockdowns while drug sniffing dogs search the private property of the students. These government institutions expel honor students for zero tolerance infractions such as carrying aspirin or nail clippers.
Now tell me again about the "freedom of expression" demonstrated in a public school via a "day of silence" for oppressed homosexuals.