Can you stop pupils from making calls, but allow them to receive calls

We are in the same boat. I’m the net admin here. Initially I disabled private chat and private meetings because that’s what I was asked to do. No communication was possible at that point beyond channel conversation. So then I disabled allow scheduling of private meetings and. That also stoped teachers from being able to setup meetings as-hoc. This seems like something that should be obtainable but I haven’t had any luck. It is also frustrating how long the policy’s take to apply and apply changes. I’ve had to manually flush clients cache in the teams app to get their client to allow chats with students after disabling it. Urgh.
Stay Healthy.