Yeah, I don't know the exact rules for transferring schools during the year, but they tend to be fairly strict.
Even if that's totally within the rules, I would caution against it. This may be a total hypothetical on your part, but if it's something you're considering, let me try to dissuade you.
One, the state-bound team probably already has nine people, which means they would have to kick out one of their own. Most teams would probably be reluctant to drop their under-achieving friend for a stranger, even one with really good scores.
Two, even if they had an open slot, a successful team probably already has good internal chemistry. A transfer from a different school will probably, in the best case scenario be what military units call an
"FNG", and, worst case, some sort of mercenary. Most coaches probably won't want to introduce those sort of variables into a formula that's already working.
Third, USAD has been know to develop new rules on the fly and implement them post facto-stlye. Even if it's legal now, it might not be fifteen minutes before nationals. No, really. If the wrong people found out, you might be
beyond screwed.