He took back the halls.
He suspended and/or expelled the disrupters.
He let the possibles know he was there to make the possible possible for them and with them.
He taught them how to eat at a table.
He established higher expectations.
He created “motivated cooperation” (aka positive competition) teams.
He eliminated the nay-sayers.

Note how he needed the support and allowance of higher-ups and the school boards to do it. Without that … nothing.