This is in violation of the "child find" mandate. They already know he has a disability, he has ADHD and ASD, right? They can't just refuse to evaluate. You do not have to accept this, you can sign the form saying "I don't agree" and take them to mediation or due process. Then they would have to prove why they are in their right to not do an evaluation in front of a hearing officer (and will probably come off looking ridiculous). What you "should" have gotten is a "Prior Written Notice" there should be a box to allow you to disagree with their "proposal" to do nothing.
I thought our district was really bad, and they fought me on evaluating DD (and fought certain testing that I asked for), but they never outright denied an evaluation. I would be furious. I would call your State Dept. of Ed and talk to someone in "compliance" and ask for advice. It's possible you can also file a formal complaint, stating that they are violating child find by refusing to evaluate a student with a known disability (they are supposed to evaluate even if a disability is "suspected", so I don't see how they can claim no disability is suspected, if you already have an outside report with diagnosis codes!)
