SRT434 is not a faith - it's a programme of teaching available to all Christian groups, no matter what their church. Furthermore, it's administered as a registered, limited company - not-for-profit, BUT ... profits are put back into administering the programme. Therefore the Playfoots can hardly hold up the ring as a symbol of faith.
Christians have long held pre-marital chastity as one of the ways in which they uphold their faith. They keep themselves chaste whether or not they declare it to the world, and they don't need jewellery, t-shirts and other money-making merchandise in order to remain that way.
A Jew will not eat pork, a Hindu will not eat beef. Some kids believe in the importance of study over all else, and there are those who have no time for recreational drugs. None of them seem to have an overwhelming need to wear cheap metal rings in order to say so.
It's not often I come down on the side of schools in matters of uniform etc., but I really hope the Playfoots lose this case.