Yes, we have been given that reason, and it wasn't even that complicated. They could not send DS to a higher grade for math in the same school because the teachers from the other grades were not teaching math at the exact same time. Another family got the same excuse (as well as the excuse that she should not be walking to a different classroom for math by herself!). We switched schools and this time the principal made sure the schedules were aligned so we can accelerate if we want to, but it has to be done before the school year starts.