FOX commentator addressed that when the video of him jumping off the roof first came out. Commentator speculated that was plan B (or A), as other people going up the way he went up.
Part of his climb up was on stairs. The rest was probably an unsecured permanent roof ladder or roof acess door.
A question would be why wasn’t the roof secure to casual entry. Might have had help there or just a very non-secure campus.
a group of individuals, perhaps including his mother,
got him roof access because HE wasn’t at the school,
just there to be one of the patsies it appears.