I got my setters and shelves at wholesale cost. That was the best price I
could find after calling several companies around the country. I guess you
could make shelves - someone has! I don't recommend it and do not know any
clay people who have.
In a classroom, I would spend money on shelves and various size posts. You
are not going to be doing tiles all the time. Extra shelves are really a
plus when firing student work. You want to fire full loads.
I would talk to other art teachers in my area about sharing special
equipment - like shelves and posts. Your clay projects could be scheduled
at different times of the year.