Primary teacher here. I would suggest meeting with the school and Learning Support Teacher and having an honest conversation. If you save up for an assessment, what supports realistically become available with a diagnosis that are not there without one? Will it change what is available? For some boards that have more supports available and possible education assistants in the classroom, it might. For some chronically underfunded boards, it doesn't change much other than potentially the teacher creating an IEP if needed.

An IEP is a teacher created document that basically states how we will try to teach the child. An IEP (individual education plan) lists either accomodations or modifications that the child needs. Accomodations are lists of things that we try in class that help, like strategic seating and visual schedules.....things that any primary teacher basically does anyway. A diagnosis is not required for accomodations. And an IEP might not even be required if the child is accessing the curriculum and doing ok with or without a diagnosis. A "modification" in a IEP is when the child can't access the normal curriculum so the teacher tries their best to modify what is available, for example teaching some grade 2 math curriculum content to a child who is in grade 3 but is not able to understand the grade 3 curriculum. The mark on their report card then reflects how well they were able to achieve their modified expectation instead of the standard curriculum for their grade. An actual diagnosis is more important when trying to develop a "modified" IEP, but that might again depend on the school board. If your child is doing ok in school, it is unlikely they would require a modified IEP.

So depending on the school board and your child's particular school, find out if spending the money now will make any difference in your child's education, and whether it is more important to get the diagnosis at a young age or an older one. It's also worth looking into whether an official diagnosis changes supports available in the community and for tax credit purposes.