I had experience working in the school system. Sadly, some schools just have it wrong.

I've seen kids placed in Special Ed due to "ADD." These kid's behavioral problems oftentimes would evaporate if they were in accelerated classes.

One student I remember distinctly talking and fidgeting and moving about the classroom. The other students were struggling with an assignment on polygons, but the ADD student was already done.

He would always finish early and usually got everything right. Did he have ADD? Perhaps. Did he belong in that class? No.

He was anxious and fidgety because he was understimulated. It was too easy for him. He was very intelligent.

Once he moved up to more challenging classes, his ADD symptoms almost disappeared entirely.