As usual, Trump is lying about being prevented from attending the graduation:

Merchan has not prevented Trump from attending his son’s graduation. In fact, when asked if Trump could be excused from court on Friday to attend the event, the judge stated that it was too early to rule on the matter but that if the trial proceeded as planned, he would be open to excusing the defendant.<

https://www.rollingstone.com/politics/politics-news/trump-high-school-graduation-barron-trump-1235005274/