Why?
It may be reasonable to deny the services to all children.
And it might be “legal” to deny the services to some children but not others, based on whether those children do other things you force them to do (like in this case, attend public school).
But why is it reasonable to you that a parent be required to use ALL of the public school services, in order to avail themselves of a FEW of those services?
What is the benefit to the state of forcing the parents to send their kids full-time to school, as a condition of getting the special service the public provides?
I can think of no reason why it is better for society or the parents to force them to send their kids to public school. It obviously benefits the NEA because they can insist on hiring more teachers, and it benefits the people employed by the government because they can get more money because enrollment is higher.
But it drives up the cost to the taxpayers, it inconveniences and in some ways HARMS the children the state is supposedly wanting to help, and will NOT save money except in that some rare cases parents will hate the public schools so much they will be willing to forgo necessary treatment for their children.
I agree with your point.
In our case, we thought the public school was not providing enough services. We are paying for those services through private school (small class size, multi-sensory reading program, extra help).
However, we lost occupational therapy and speech therapy that everyone agreed my daughter needed.
In public school, she wasn’t learning how to read and write well, but we can’t afford occupational therapy which would be helpful. Our insurance is providing speech, so we are lucky there.