Oh my goodness, have we BTDT before! We've heard it all. "She needs to really know the basics" and "we need to fill the gaps" and "she's only bored because you taught her too much at home" -- just imagine you can see my eyes rolling and rolling and rolling. Beast Academy and Dreambox are both fine and, in fact, the best of all the online edutainemnt things we've tried. There's no reason they wouldn't be appropriate. Your teacher probably doesn't even know what Beast Acadmey IS.
You're not being pushy so much as that your teacher has no appropriate expereince to understand your child or your child's needs. Your child is statistically unusual and she hasn't had enough kids like him to "get it". Just keep doing what you're doing and keep asking the school to accomodate. Maybe this one won't, but maybe the next one will. The best luck we've ever had with accomodation is when the teacher is on board, but IME it's almost impossible to change the mind of anyone who isn't willing to think outside the box and be flexible.
