Some schools do make offers on the spot. D received one of these.
Some schools call or email shortly after the audition with an acceptance offer or within the next day or two. D received a couple of these.
Some schools let you know after 1-4 weeks.
As noted in a previous post, sometimes you are put on a “hold” list until their audition process concludes.
Sometimes you get redirected or told you are accepted “to the theatre arts program” (which turns out to be a redirection or BA acceptance at a BFA program). Some of these letters can be somewhat cryptic to try and decipher.
Many/most schools begin sending out calls/letters/emails/web notices in late February or early-mid March.
A few (seems like fewer each year) make you wait until April 1 or the last week of March.
Then, of course, there is the dreaded Waitlist. D ended up on three waitlists. It was not very much fun.
Note that for some schools the earliest notice will be a posting on their student portal. In some cases, these can be somewhat cryptic to decipher, for instance, your “Desired Major” changes from “Theatre Non-Specific” to “BFA MT.” Or the other way around (gulp).
Some schools do acceptances and rejections in waves. Some will leave students “hanging” for several weeks after their initial letters of acceptance go out. I think some schools do this to gauge what their yield is looking like before accepting more students - so it may be a kind of “hold” status. Or not.