Depending on the curriculum, a shooting school requires students to fire somewhere between 500 and 2,500 rounds. While ammo usually can be purchased on site, it's stocked there as a convenience for students, and is priced accordingly. You can give your student a better deal.
Factory generic ball ammo, or top-quality remanufactured (commercially reloaded) ammunition like that offered by Black Hills is a good bet. On my last trips to Thunder Ranch and Chapman Academy, I had thousands of rounds of 9mm Black Hills shipped ahead to the schools. There was no bobble, and I was delighted with the performance of this cost-effective ammunition.
You can save your customer extra shipping charges by drop-shipping the ammo from the factory to the training facility.