I just listened to the whole thing with the score.
The biggest thing that would worry me is how exposed all of the woodwinds and brass are throughout. Almost every instrument has completely exposed solos, so you need strong players in every single section. This is the kind of thing where practicing only takes you so far, you need to be at a certain level of instrumental mastery for it to be a reasonable undertaking.
The trumpet part is pretty hard in spots, and I might not expect a high school level player to be able to play it with any consistency. In particular, the trumpet solo at rehearsal 4 in the first movement, and the triplet fanfares throughout the third (such as at rehearsal 42).
There are some individual nasty measures for upper woodwinds and strings sprinkled around, but I would expect high-level high school players to be able to work them out given the length of a typical high school concert cycle.
Overall verdict: If it's a really good high school orchestra, it's doable, possibly with hiring a ringer for Trumpet 1. Otherwise it would scare me.