You can assign default pay rates to a service for each teacher (ie, 'for this service, when this teacher performs it, pay them x').

To do this, click Appointments > Services > click the service.

Next, click the services' dropdown menu > Edit pay rate

This pay rate will now auto-fill when scheduling this teacher to perform this service. Once you select that teacher, and that service, the scheduling form will automatically add the default pay rate you chose.