I think the idea of a Reef Tank in a Highschool Science Lab is great. The chemistry necessary to start and maintain a Reef Tank is really extensive. I do not know what your plans are for the tank but I can see many possibilities and learning oppertunities. If I were you I would put a call out here in R2R as well as to the manfacturers for various test kits, I know that I would be happy to send you one of my fresh as yet unused API Master Reef Kits and I have no doubt there are others who would do the same.
Testing and understanding the cycle and the chemistry of the reef enviroment would be a great way to brng practical real world chemistry and biology into the classroom, allowing the students to test the water and understand the chemistry which goes into the test as well as the results will make the lessons far more interesting than sinply a book and lecture.