The instructor is talking. Be quiet.
The students are practicing. Be quiet.
The students are playing. Be quiet.
Watch quietly, cheer or laugh or applaud when appropriate, smile at your child no matter how they perform.
Or wait outside.
Waiting outside is a difficult one. I’d be inside watching. But I’d just watch. Sometimes a child will do something impressive, then look to his parent for approval, and they weren’t paying attention.
If you’re going to be there, be there. But be quiet.