I have done a lot of work teaching woodworking, with children, ages 5 to 18. It can be nerve wracking at times, because the supreme goal is to send the child home with no puncture wounds or trauma. The product is secondary. This intense emphasis on safe procedures requires close supervision. When compared to time consumed, very little actual work is done.
The bill is written specifically to relieve the employer of "in locus parentis", which is the burden of the school. Under this legal doctrine, the parent hands over the child to the school, who is now responsible for their safety and health, through all acts of commission and ommission.
In other words, if the school does something, or fails to do something, and the child suffers, the school system is legally liable for damages.
Take away this exemption from the bill and watch it evaporate.