OK, so I'd start with the positive that your school has over some other schools - they are clearly recognizing that the students do not all learn at the same rate or in the same way. Also, I am impressed - we have no such gifted magnet!
Still, it sounds like the "execution" is poor. The school is on the right track (I always like to start my requests for change with pointing out what they are doing right!), but grouping/"cluster" is worthless unless they follow it up with some differentiated instruction. I would definitely approach the school on how they "differentiate," perhaps armed with what might be excellent school policies on how gifted children should be instructed (check your school/district/central website or directory). Is this school following its own policy?
