I’m not allowed to do negative reinforcement, students aren’t learning.

I teach several group music classes of around five students each, ages 3-6. They get stickers and prizes for doing a good job, but I’m not allowed to withhold stickers or prizes. Because of this, my students have learned that they can pretty much get away with anything and many of the classes have become almost or completely hostile to learning.

I am supposed to offer them an extra sticker or offer them a prize at the end (which they get anyway) if they behave. Kids yelling, banging on the piano, refusing to listen or pay attention, being rude, etc. I can’t do anything about it. I’m trying my best but I feel like I should be better. I started back at the beginning of the school year.

Is it normal for kids this age not to be disciplined? My boss says we don’t want to traumatize the kids. At these ages, should they be given rewards regardless of their behavior or should rewards being taken away from them? Also if you have any advice on what to do here please let me know.