This discussion about school buildings is brought up fairly often, but I am not sure several posters have any idea how that is feasible. Sure, if you are building a new school it can be designed into the spec, but it would be a difficult, almost impossible undertaking in the old school buidings up and down the land.
DH looked into it (his job) for independent schools, where money is more readily available, but the ducting needs to run through the entire infrastructure and fabric of the school building. It isn't at all like installing air conditioning, let alone the huge costs involved.