I teach in a school with 91% free lunch, school provides instruments. I wish someone had told me (actually they did, but I wish I had listened) to call the parents when their child is being disruptive. I NEVER called home my first year. 2nd year I started calling in October and behavior improved dramatically.
Don't ever bully your kids, be the adult who is following stated policies and procedures. You have been tardy to my class 4 times, that means I have to call home and assign a detention. Nothing argumentative about it, just that's the procedure. Be consistent. And don't get dragged down by bitter old farts on TYB.
If you're new to an established program and you're the 2nd assistant, you're fine. If you replace a beloved director in a one man gig, you'll have trouble getting kids to buy in to you. In that case, focus on setting clear expectations and holding students accountable. The ones who don't like you will graduate and your life will get better.