This is the chair used in all the APS elementary classrooms I have ever seen. Made by Virco, it is the hardest, most uncomfortable, most dangerous seat on the market. Cost: less than $40 shipping included. It is guaranteed by the manufacturer to last at least 10 years. I dare any adult to sit in one of these for 182 days each year for the 6 years of elementary school without going crazy. They actually do make your butt ache.

Also, the splayed legs (built that way to discourage students from leaning back in their seats) are really dangerous to others considering most kids are asked to turn the chairs upside down at the end of the day and put them up on their desks. Those legs do poke other kids in the face.

I would consider some sort of softer, safer chair made out of resin: it may not last 10 years, but would do a lot to improve the concentration skills of many children.