You have to assume that tampering rules still apply. If any of those "elite" schools start recruiting players before they hit the portal (ala Linguard), there should be severe penalties.
They should net out the transfers and add (or subtract) the difference to initial counters. If you have five transfers out and three transfers in, they should allow the incoming class be 27 (e.g., 5 - 3 + 25 = 27).