You put down your $100 deposit for your next choice school by May 1st. All the schools know that things shift after May 1st, so they understand if you get taken off a WL and decide to go to that school instead. You SHOULD NOT put deposits on more than one school…
Also, if your child has multiple acceptances and they know they won’t be attending certain schools, let them know ASAP so other people’s children can come off the WL for that school. Be courteous. 