The question I would ask myself are...
1) Are they happy?
2) Are they learning bad habits.
3) Are there other less tangible things they are learning?
Particularly in early elementary school is about more than learning math & how to read. It's about getting along with other kids, working in groups, listening to the teacher, following directions. They may be working on handwriting, art, and music.
I think this really depends on the kid & the environment they are in. I personally feel strongly that preschool should be play based no matter who you are. My son taught himself to read at 3, yet was very happy in his pre-school/daycare because they weren't doing anything academic. This changes IMO when you go to elementary and gets harder the older they get. But depending on the program they are in you can challenge your child outside of school, while they 'coast' at school and gain other experiences being with other kids. It all depends on their personal experience with it.
For my son there was not G&T program till 4th grade. And yes until they the kid was mostly coasting.
