Change is hard for everyone, so the first thing I did was ask for their opinion. “What does your ideal classroom look/sound/feel like?" Here are two examples of what I heard:
"Looks like everyone working, sounds quiet so that people can focus, and feels like home" - Grade 5 Student
"My ideal classroom is like a second home, where people don't interrupt, and it's fun" - Grade 6 student
The best part of this exercise was I could give their words back to them. When I enforced my expectations I could bring it back to what they told me, for example when they were getting too loud, I would remind them that THEY said they need quiet to do their best work.
Wish me luck!