I use veyon in some of our labs and it works well. You can install veyon master to the teachers machine and client to all student machines. It requires the users account and password in order to open veyon master (so that students can not open it). You basically configure a class on the configurator on the master version using machine name or IP address (we use machine name and it works well). We do use 2 screens at the teachers desk so one for them and one to watch students
Regards