I'm sorry that this happened and I don't want to hurt any feelings. I think that the decision to start raising chickens needs to be made by the family. I think that hatching chicks in the classroom, while a great learning experience, can put people in the same position that they may be in when they sees easter chicks and ducklings and they "have to have it" and "will take care of it" and they impulsively purchase them. Planning and forethought isn't put into the decision to raise chickens and the long term needs of the bird are probably not considered.
It does seem like you were lucky to have some families that are being very responsible and already building coops for their birds. I do hope that the families were able to either adopt more than one or plan on purchasing additional chicks since they are flock animals.
I used to work at the SPCA when I lived in Florida and, sadly, every spring we would get about 100 chicks brought in by teachers that hatched them in the classroom, we were in the suburbs and not equiped to deal with them and they were not legal to own at the time in the area. Most were fostered by staff for a few weeks, including myself, and then they were picked up by a person that owned a lot of land several counties away. The chickens were basically just free range there and I have no idea how many would survive. This was basically the only option other than euthanizing all of them. This experience put a bad taste in my mouth about classroom chicks as, at least then, there never seemed to be a plan for them once hatched.
With the situation, there would not be any laws that were broken. Proving that the dad intentionally put the chick out for the dog to eat would be impossible. But because chickens are livestock abuse needs to be deliberate and intentional. Many people feed live animals to different types of pets (snakes, fish etc) I don't think that they would typically feed chicks but....
Again, I don't mean to hurt any feelings, just want to give my viewpoint. I am very sorry that you and the children had to deal with this.
If you choose to hatch eggs in the classroom again, why not see if you can find a local breeder that hatches out their birds and you can return the chicks to the breeder once hatched? That way the kids get the experience of watching incubation and you don't need to deal with finding homes for them. I'm not in your area but I'd be willing to "donate" eggs in that situation if asked.