@Zone2NorthLondon I agree, as an educator who worked in roles which involved visiting various schools I seen a lot of this.
Not everyone can join the PTA and the fact if this is happening, it's definitely wrong so more people piling onto the PTA to secure preferential treatment for their child wouldn't solve it.
Important to note, the PTA parents are often the ones in a position to choose to work part-time or not work at all.
A PP suggested it might be because those kids are seen to have more supportive parents but I don't altogether buy this. I think when this kind of unfair bias occurs it's more linked to rewarding the more involved parents who help the school out. And they are also the type of parents to create a fuss if their child is given a silent part.
There are very capable children whose parents aren't in the PTA who need very little input from parents who would learn lines or be the captain of the school sports team etc fine.
And if they are really doing it for that reason that would discriminate against a range of children including ones from troubled backgrounds which isn't fair and replicates the kind of inequality we are seeing in society.
If teachers genuinely feel there's issue where the child won't get as much as support as they will need, they can always try and work around it and put in that additional support including setting the child 'homework' to learn lines.
I used to work with children in care, and some of them didn't have the most engaged foster parents, and their biological parents had limited contact.. I'd have been horrified if a teacher passed them over for a role or position they were capable of because they didn't have the 'right' parents.