The government has got itself into a right old mess over this. Something is either legal or not legal. I think we all grasp this. Jumping off a fifty-foot cliff into the sea may be risky, but it's legal.
As I se it, it's not the going that's illegal or dangerous - it's the price tag for coming back. I'd replace the categories with:
RED = GOLD. £1,750 per person for a stay in a crap hotel watching daytime TV (probably extra), plus about £350 in tests, plus pariah status.
AMBER = DARE-YOU. We can turn this to GOLD anytime we feel like it. Think you're clever? We'll make new rules before you've had your first Mythos.
GREEN = OH, GO ON, THEN. There's nothing in the school rules that says you can't eat chocolate biscuits. But we won't like you. In fact, we hope you get Herpes so we can say "We told you so."