I have had them done by the school for my son (who has verbal skills) and privately for my foster son who has no language... the school's process and evaluation was by FAR MUCH better, throughough and accurate than the private eval. the school AAC coordinator really wanted to see where the weaknesses were and what would work...she observed, she directly tested, she read records, she tried many different types of materials both low and high tech, and made accurate suggestions for device and how to use it and for low-tech materials to assist with his language skills for a variety of functions.... the private evaluator came with one device and showed my very eager to please and high imitator foster son to push an icon and they would blow bubbles....for one hour..and the button didn't even say 'bubbles'...she recommended a high tech device with tons of vocabulary for a child who doesn't understand any language and would only push the button when shown to push the button. Anyway my advice to you is to take your concerns to the school district, be specific with area of needs and that you want an evaluation to see if AAC (low or high tech) would be appropriate (not "best" ideal") to help your son "access grade level curriculum" more easily.