I would think it would affect achievement scores to a point. Certainly there is going to come a time when a kid says "Enough!" and rebels. A lot of damage can be done over the course of those years, and it may not really show until it's bad!

A well-respected local expert who works with SENG gave a presentation about perfectionism, and I asked him if ND kids under parental pressure ever demonstrate that nutty wig-out behavior of GT kids that comes of intense frustration with not being able to match externally what they envision in their minds. (I asked to help another woman, who was wondering if her 4yo child, who was going through some intense perfectionist moments, was gifted or not.)

He said that a gifted kid who is a perfectionist usually gets frustrated and wigs out at a young age--preschool or before--whereas a kid under intense parental pressure to be perfect usually sticks with it until high school age before cracking. Until puberty, the pressured ND kids want the parental approval. But when they are ready to rebel, look out! Then they crack HARD!

YMMV by a mile, naturally, and certainly some GT kids never experience perfectionism at all. But it struck me as interesting at the time and seems germane to the conversation now...

Kriston