I would rather not, as I’m a bit overkill in wanting to protect my identity online. But it’s one of the of the three schools the OP mentioned by name.
This 80% is pretty reasonable. My guess is that it might be higher where sports that follow an early recruiting timeline (like lacrosse) are big, as some kids commit to do a PG year as early as the start of their junior year, with their committed college “placing” them at at a prep school to spend a year.
I should actually amend my previous statement. At least 80% were either committed, or had narrowed down their list of offers and generally knew where they’d end up. The only sport where kids could be actively improving their recruiting stock in a meaningful way during the season seemed to be football–one player came in thinking he’d likely end up at a NESCAC or in the UAA (Chicago and WashU’s conference), yet had multiple Ivies to choose from by the bowl game.