To piggyback on this, where does your high school hold the graduations? Our school use to hold it at the Tampa Convention Center, but later moved to the USF Sun Dome (cheaper venue). Each grad does receive a limited amount of tickets as well due to not enough seats for everyone.
Most of the schools in our area use the same downtown theater/auditorium. Since DDs class is smaller, they each get 10 tickets. Other schools where there are more grads get a lot fewer tickets per person. We don't need 10 tickets, so we'll give away the extras to anyone who needs them, if there is anyone!