i'll answer the questions put to me, then i'll be off, this thread is really going nowhere.
in my view, the benefits of collective worship include the opportunity to hear stories and parables or fables with a moral and to think about the moral of the story. this could be from the Bible or from elsewhere, since the worship is only meant to be 'broadly' Christian. This is the kind if thing i recall from my own schooldays, and may well be part of what helped form my udeas of right and wrong.
in my dc's school, assemblies have been themed in the past, for example around friendship. That has lots of value in a school.
Bowing your head in quiet contemplation or being thankful is an opportunity to be alone with your thoughts on a busy day. Nobody ever forced me to pray, and since they've no idea what's going on in my head, i dont see how they could have.
its also a time when several year groups collect together, an opportunity to see what older and younger children in your school might be doing. this can help form vertical relationships, which are very valuable in schools.
i dont know anything about Open The Book, they dont operate where i live.
as an athiest, obviously i dont agree with the message that God is everywhere. But ive no problem with kids being told that, because its very easy for me to say to them, yes, some people believe that, but i don't and neither does your dad. That's life, people have different beliefs and we should respect them.
recall the reason i said you haven't taken on board the views here is because at 2am, 300 odd posts in, you were still as hysterical and angry as you seemed in your op, and that made me think your thinking hadn't moved on at all. apologies if i got that wrong. but you asked in your op for advice on how to deal with it or handle it (sorry to paraphrase) but didn't seem to listen to those who said either a)dont sweat it or b) withdraw your child, I do, its fine. You're still asking why its happening, despite knowing the answer.
i don't really think i got such a hard time here Mehita, but thanks for your support. Its very interesting that you and i seem to be of the same mind in so many ways, except for our diametrically opposed belief systems 