It was reported that

[Ocelot II]

1. Trump would love to go to the SCOTUS argument, just to sit and glower at them

in the hope that he could remind the newest three who appointed them. I doubt he gives a damn about his son's high school graduation, though - he probably couldn't pick the kid out of a lineup - but he wanted an excuse to avoid going to court. He would have used the day to hold a campaign rally; he probably would have used the graduation itself as a campaign rally.