Most countries I lived in don't prompt either. (And in Germany, people would be out on the streets if a school did that kind of prompting.)
http://webarchive.nationalarchives.gov.uk/20130401151655/htt...
"Since the 1944 Education Act, re-enacted in all subsequent Education Acts, there has been a statutory requirement that all maintained schools must provide a daily act of collective worship for all registered pupils, unless they have been withdrawn by their parents. The Education Act 1988 removed the requirement for this to take place at the start of the school day. Collective Worship can now take place any time of the school day."
In practice, the law is widely ignored.
NB: I went to CoE schools for 7 years of my K12 education, and came out an atheist. I think part of it is to do with the teaching - even at a church school, we were encouraged to question everything, and had at least an hour a week where we learned about other religions in a very objective light.
I believe that on many levels, education comes down to that learning to question - and when you're told to believe things unquestioningly, you're intentionally breeding ignorance. My take is that it's not so much about schools having prayer etc, but the way they encourage thought. Kids are smart; if they're allowed to think for themselves, they will.