Several good aspects stood out:

I agree that your locations were well selected. The catwalks, the garages, the alleys - all helped the mood and put us right there in the danger.

I think Batman's cape was exceptionally good and the most effective costume piece. The shots that just included the mask and the cape were the most effective, so it was wise of you to choreograph his fights to primarily feature those two costume pieces.

I really like that it is silent. No need to be bogged down in who these East Side Skulls particularly are. They're a gang. They're bad. The leader has a scar on his face. Perfect. That's all we need. No slow dialogue scenes either. Since it's a short fan film, let's just see Batman knock some heads!

Very clever use of camera when the batarang pierced Skull Leader's hand in the end.

Tighten the editing and redo the soundtrack with sound effects and original music, and it's a fantastic high school fan film!