You may wish to disable chat rooms in your teacher's Zoom account. To do so, navigate through your Zoom app (or online portal) to your Meeting Settings. In there, scroll down to the heading "Private Chat." Make sure the toggle is turned gray. This disables the Private Chat Function. (See image below)

Since that is the solution to disabling private chat, I'll go ahead and close out this ticket. However, if further assistance is required for this, feel free to reply to this ticket and it will be re-opened for further investigation.