Welcome!
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we need a student advocate as soon as possible, but I don't know where to look for one.
Parents are often their children's best advocates. Have you seen the Guidebook on the Davidson Database?

More advocacy tips:
- In this recent thread, several posts discuss reasons to not use the word "bored" when advocating.
- While in general there is good and bad in everything, a focus on negativity and disappointment may be seen as smacking the oobleck with a spoon and creating an unyielding solid... it works against advocacy.
- Focus on the positive, on the ideas set forth in the law and in school policies, and how the school can implement these to help meet your child's needs for intellectual peers and an appropriate level of academic challenge and pacing.

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recommendations for private psychologists for testing
Lists on Hoagies' Gifted Education Page: Psychologists, Professionals.

You are on the right track. Testing is the best place to begin. Without test results, it is difficult to show your child's brain is out of the norm and therefore your child's educational needs are out of the norm. While schools may increasingly rely on their own testing, private testing may be more in depth and provide greater insight.