Not all children react that way. Some, especially girls, just fade into the class. Think about it - the squeaky wheel gets the grease, and the child with behavioural issues gets the testing.
This was my DD. She tried very hard to conform to her teachers' expectations of her, even going so far as to pretend not to know things she'd mastered years before.
Luckily, she has very squeaky parents.
It is not just girls that fit this profile... even though DS is only 3.5, we already seen signs that he will fade into the perceived age level behavior and disguise the full extent of his capacities. Every single teacher/coach always told us how he fits so well regardless if the room is full of boys or girls, and how girls love how calm and mellow he is. We had one teacher mention to us that if you did not pay attention, you would not notice how smart he was because he is so well behaved and blends in so well (and I don't think she even realized the full extent of his mental capacity). We were so surprised that even at 3, we would see this fading into the background (and major signs of boredom that the teacher had not noticed since he was very subtle in how he handled his boredom behind the teacher's back) - we are definitely keeping a close eye on his younger sister too, but I have a feeling she will be the squeaky wheel.
So we are already trying to learn all about the options we have and dealing with the fact that even at this young age, we have to keep a close eye on daycare/preschool and make sure they are where they belong, and not stick strictly to the traditional age groups mindset.
