We fought this battle in my area about 25 years ago. At that time, it was thought that students HAD to use the "school photographer." In fact, the school cannot dictate where students spend their money. They can, however, demand YEARBOOK photos be made by the "official" photographer, but, if they do, it must be free. The contract photographer is providing a lot of concessions to the school. In exchange, they can demand a shot at doing the seniors, but that's it. We had to educate the buying public that they truly had a choice. There are at least two schools in my immediate area that insist seniors be photographed at the school by the contract photographer. Most will then go elsewhere for portraits for their family and friends. The school, of course, cannot provide the names and address of the seniors. Here in the states, a fairly accurate list can be purchased according to postal zip code. One local school provides students with a list of studios that can provide photos that meet yearbook publishing specs. I really think you're sitting on a wonderful opportunity.