My generic answer to "when do you push the school?" is, "when it becomes necessary."
Answering this question means evaluating how the current situation is affecting your DS. Does he like school? Does he like his teacher? Is he making friends? Is he displaying adequate work habits? Are there any behavior issues outside of normal age-appropriateness?
If school is still a positive or neutral experience for him, then it's no emergency. Otherwise, the more negatively it's affecting him, the more fiercely you should be pushing them.
