@Alessandro ********
if it's the original 90 days on the ED visa both the school & your future employer are both wrong.. 😕 🙁
You are allowed to stay the 90 days once that visa is issued whether you go to school or not AND it can't be cancelled at the immigration office. Only extensions can be cancelled,
You stamping out of the country is how a 90 day admitted until stamp from an ED visa is cancelled 🙂