You can register with Airsupply and another agency. If you are already under contract through an agency to do supply work with a school you must honour this contract. After your contractual period is complete you can accept supply work from wherever you chose. You will only be able to work with a school through Airsupply if the school has signed up with us.
If you already have a recent pre-existing relationship with a school through an agency (i.e. you have worked at the school through another agency recently) and you get offered a permanent role o a long-term supply contract, your original agency may theoretically ask to be compensated by the school. This is something to keep in mind, we would be happy to discuss your particular circumstances, please call us on 0330 122 6629.