Stuyvesant has open house dates up on their website:
They are Tuesday, 10/10 (Manhattan, Staten Island and Brooklyn) and Wednesday, 10/11 (Queens, the Bronx) - both from 5-8pm.
Keep in mind, things can always change so no matter what a school’s done in the past, they can always change it up. Stuy has a newish principal who might have a different way of doing things. And if there’s a conflict with another tour you can attend either day of Stuy’s open house.
These are open houses in that there’s no registration necessary, no check ins, no sign ups but they’re also tours. Once you’re in the building you generally hit the auditorium first, where they hear the principal and others speak, and then move throughout the building with student guides who take you on a predetermined tour. The lines to get in a pretty epic but I’ve never heard of anyone not getting in. My daughter actually had a test prep class same day, didn’t get there until 7 and had a private tour as the school was far emptier than earlier. My son and I were online an hour or so before the open time and we were in the first group to enter.