I get it. We do want to protect our kids. However, in an interview, the mother in this case implied she was going to seek legal action against the school. I'm sure getting the local news to report on the case will be enough to make sure the school pays more attention to its policies, and that means legal action would really be to make money off the injury, and I'm not totally sure that's a good use of taxpayer money.
Kids will get hurt at school. I ought to know. I tore the labrum in my shoulder during football practice, and I got some ice. I also broke my ankle in gym class and walked to my car and drove home. I tore my ACL and MCL while playing at a school gym, and I continued playing the game, unable to do more than stand in one place. That all sucks, and maybe it sucks more that no one was there to give me an X-ray or MRI.
Having been a teacher for a number of years, I probably saw a few injured students when they came back from gym class. I saw ice packs and whatnot, and I usually told the kids to make sure they got the injuries checked out by a doctor if it still hurt later. Since I was not a practicing doctor, I never made a diagnosis, and I never figured it was my responsibility to call home, figuring the kid (I taught high school) would have the sense to know.
Granted, the child in this local case has a disability, and that could affect her ability to assess how she feels. That said, the course of action is still generally to ice an injury, and I know from my injuries that a sprained ankle can hurt as much as a broken ankle, so it's really hard to say that a teacher should have known this particular student's wrist was broken.
The main point is that if you're a parent, you should expect your kids to get hurt. You should be ready to visit the ER or doctor when it happens. Generally, you should be glad it was a broken wrist and not a broken ankle. You should be ready to do all these things because you are the parent. Kids need gym class and physical activity, and that sort of activity may lead to injuries. I am sorry this child had to suffer through an injury, but I really don't think the local taxpayers want to pay this mother for doing her job as a parent.