'You don't have to send your child to a C of E school, but if you choose to, you should accept that it is a C of E school'.
Except that for many famies, the only state school available is a C of E school. OK, they could move house, or home educate or start earning enough money to send their child to an independent school, but I wouldn't describe a parent who sends their child to the only state school for which they are in catchment as making an active choice to give their child a telion-based education.
And the religious worship requirement applies to non-church schools, too.
Does it harm the children? It did me no good when I was repeatedly told by teachers and visiting speakers at my school that many of my loved ones were sinners who would suffer torture in hell for eternity. It wasn't great for my friend with a disability who was told that God had chosen to make her suffer. It's also been quite hard for the people I know who had pretty grim experiences of religion in their own childhood to be pressured by their children into attending church services.
I think that well-taught RE is a good thing, and that a familiarity with Christianity is of great benefit, not just to those with an interest in theology, but also to anyone who wants to study Wedtern literature, history or art history.
But the requirement for worship of a broadly Christian nature in all schools doesn't reflect our society, and I think it does more harm than good.