I see just two issues when school intervention is acceptable.
1) When a parent is engaged in abusive behavior against their child. Not just scrapes, bruises and broken bones, but obviously encouraging children to engage in very unhealthy or destructive behavior, such as smoking, drinking alcohol or taking illegal drugs, or overeating to morbid obesity.
2) When a child might have a serious medical problem that the parents are unaware of or do not realize threatens the health or even life of their child and/or the other children. For example, it is legal to exclude children for not being vaccinated, for actually having infectious diseases, for body lice, when they have untreated asthma, or even psychiatric problems that cause them to lash out at others.
Just sending a note home that the child either needs or may need medical help is surprisingly ineffective. Often parents have neglectfully ignored their children’s problems, or even contribute to and encourage such problems. Only with the coercive threat that the child may not return to school without a doctor’s note is enough to punch through the neglect, in that children must be educated by *someone*, by law.
Seriously, schools only do this when the situation is borderline to contacting the state child protective services. A whole lot more coercive than needing a doctor’s note.
A majority of states have both medical and religious/philo or conscience exemptions to vaccination. IIRC the only way to exclude an exempt child from school in most of these states, is if there is an outbreak and a state emergency is declared.
Your posts read as if they were the point of view of a conventional pediatrician, or possibly child protective services?