If people need reasons to uphold a masquerade for the duration, here's a few. Anybody going to school will have rumors spread about them pretty quickly if they go off-script. This probably isn't "alien invasion" levels of bad, but it can be embarrassing and troublesome for a long time. Leo needs to attend school regularly, and do well, to uphold his bargain with AEGIS. Jason Quill must make public appearances, and his "brand" (the Foundation, any charitable work his family fortune is providing for, etc.) is vulnerable as well. I see no reason not to tell his human assistants and staff. But... Jason also has access (via biometrics, but also I assume by virtue of just being Jason) to his household's computer systems. The smarter AIs might refuse to accept commands from somebody who claims not to be Jason. Not-Dad in particular has already shown that he won't grant access to an important and useful thing simply for this reason. Retaining access to these AIs is probably important. It's possible that Harry's family has committed him to after-school appearances or other activities for charitable purposes, e.g. mall openings and the like.
