How much fits into each kiln? Can students be assigned to assist in loading/unloading, or get extra credit for helping? How many pieces is each student expected to finish each term?
If the firing schedule is the crunch point for your program, perhaps reworking your curricula would help. Can you incorporate exercises like ' thrown x number of cylinders in y time", where the students are busy, but the pieces are recycled? Can you have a size limit on pieces, like airlines have on carry-ons? Would it be possible to do some pit firing, to take a load off the kilns, as it were?
If you have product ready to go that othewise would sit in your house/studio doing nothing, and you can afford to gamble $250.00, go for it! Write and attach your own price tags, or get written confirmation of the prices before the start of sales. Keep your own inventory list, and check any unsold product against it and sales receipts. Agree on a policy concerning breakage-who pays, how much, etc.
Write it up as a contract, get it signed and see if you can sell your wares.
If the seller won't give you a signed contract, walk away.