Welcome to our world. Glad you found us---sorry you had to.
I understand why you would be sad about the diagnosis. It sounds hopeless but it isn't. I notice you are from Canada. In the states, the incidence of MMI (mild mental impairment) has dropped radically in the last 20 to 25 years. The reason is there is a corresponding increase in children diagnosis'd with Learning Disability (LD).
For some reason, most people feel that parents and teachers can "work with" Learning Disability (LD) but MMI (or MID) is "immutable." This is not so. An evalaution, even a very good multidisciplinary evaluation by highly qualifed professionals, is just a snap shot of where the child is right now. A child as young as yours has great potential to change and improve. IQ is not really very stable until adolescence after which, if the testing is valid, few huge changes emerge in most cases, but even then, there is still room for growth.
I am not familiar with Canadian law but you have many rights similar to those that are the "specialty" of this section of the board in regard to U.S. law. I would encourage you to try to get the most stimulating education possible for your child so as not to let this diagnosis become a self-fulfilling prophecy. If you want to post about your child's particular learning and behavior needs, probably some of the members (whose children are labeled Learning Disability (LD)) will have suggestions.