To be honest, with the kind of home enviroment that can result in children being sent to faith school (ie deeply dogmatic faith) the kids are going to believe in creationism any way.
An exception occurs when the local comprehensive is of abysmal quality, then for the sake of the kid's exam results some parents will send them to a faith school despite not being actively religious.
Other reasons exist - my entire family used to go to Sunday School and sunday lunch was then spent with my parents picking the lesson apart.
As soon as people asked, they could stop going.
Likewise, my girlfriend went to a primary school run by Catholic Nuns. This was in Vietnam and her parent's reasoned the religious indoctrination was easier to counter then the Party's.
The bizarre state of British Faith Schools & Creationism
Moderator: Alyrium Denryle