You'll do your customer a disservice if you sell him a floppy fabric holster for his shooting-school training. Such holsters are designed for casual wear by plinkers and hikers who don't have to draw fast or reholster their weapons in a tactical manner. At a shooting school, your customer will constantly be drawing against the clock, and be expected to reholster one handed by feel.
There is a lot of good leather in a wide and acceptable price range to offer your customers. Look to Alessi, Bianchi, DeSantis, Don Hume, Galco, Gould & Goodrich, Ted Blocker and others.
There is one caution, however. Good I leather takes time to break in. If your customer is going to a school in six months, no problem; there's ample break-in time. However, if he's leaving next week, that's a problem.
For the customer departing for a school on short notice, think "plastic holsters." The Safari Laminate from Safariland is good, as are any of the top-quality Kydex holsters from Blade-Tech, Ky-Tac and Sidearmor. If price point is critical, a $20 to $30 holster from Fobus or Uncle Mike's will serve the student well.