I think you need to be very cunning and play them at their own game. Catch them out, and make sure they dig their own hole.
Let's just pretend that the school commissioned this test. Ask for a copy of the test results. The assesment. Ask for a copy of their conclusion, analysis, recommendations.
If they refuse, one has to question the school on what on earth their goal was by commissioning this person who then gives no recommendations. Then take this forward, expose the school for the idiots they are.
Ask for a meeting. In person. Then turn up with a person that's weren't expecting, eg your mum. Once you have a witness and there are 2 of you, and only 1 of them, they'll hate it.
Play the game. Cleverly.