You can only request an evaluation once each year BUT there are also all sorts of rules for transferring students.
I would send a certified letter asking for an evaluation of difficult child's learning and behavior problems. If the SD says, "no, one has been done," then I would ask to have the result reviewed at a meeting in this new SD.
Do you have a complete set of school records? If not, request those also in the certified letter. You have an absolute right (or your husband does) to these records. If the receiving SD has incomplete records, then they have nothing to base a denial of service upon.
Start a really good filing system and remember RULE #1: SEND ALL MAIL TO THE SD CERTIFIED.
Martie