I found a link to information that's blunter than what blackcat found:
schools must evalute by law.
This is an interesting way to frame a question – Can a school be “forced” to something they don’t want to do?
Does the law require the school to evaluate a child? Yes.
You may wish to send an email or letter to numerous people (this sort of thing has to be in writing). State that as per section xxx of federal law, you requested an evaluation and that it was refused, which is a violation of the same law. Note chapter and verse the way Wrightslaw does, and ask why they're failing to comply with the law.
"A State educational agency, other State agency, or local educational agency [school district] shall conduct a full and individual initial evaluation ... either the parent of a child, or a State education agency, other State agency, or local educational agency may initiate a request for an initial evaluation to determine if the child is a child with a disability." 20 USC 1414(a)(1)
