laffy do I work with you?!
I do think there's a correlation between PTA members and their children getting put forward for things. But generally, this isn't a result of them being PTA members as such. But it's a result of them being involved in the school, supporting the school, and pushing their children to achieve.
For example, a lot of PTA children are on our sports teams... The PTA managed to get the sports club started, they are the parents who can be counted on to bring their children for matches etc.
The PTA children are often confident and organised, they probably picked it up from their parents who were confident and organised enough to go for the PTA.
Unfortunately a lot of children miss out as a result of their parents not being interested in school. They might not do things at home (not necessarily homework, but reading with their child, practicing counting while out and about or just talking to them about things they do at home). They might not bring their child back to school for sports matches or drama performances etc.
Please note: I'm not saying that all non-PTA parents are not interested in school! But PTA parents are and that must rub off on their children! and if you go looking for confirmation that PTA children are favoured, you'll find it. Whereas you might not notice Joe Bloggs getting several awards (because he's doing well despite his home life) because you weren't looking for it. Hope that makes sense!