This time is the first that I've had a teacher ask any of my children directly for money to replace school properly without some sort of contact with me or another parent.
As far as I know, the teacher doesn't even own the chair. I have no trouble going to the office and giving $3 or $50 or $100 to buy a new chair. I'm not sure how ownership of standard classroom equipment goes. I hear teachers have to pay for a lot of things on their own, but I expected that chairs in the classroom were provided by the school or the district. If it is the school or the district that owns the chair, I'd prefer my son to go to the office with the money to pay more directly.