Our students are covered by the school rules as well as our rules, which is 'no excessive pda' and we also don't let them couple up. So when they're going anywhere outside of B block (where our build room is), or when we're at competition or at an event - they have to stay in no less then groups of 3. It works for us.
IF it became a problem we'd pull the students aside and talk to them privately about it. It's not something that we'd do in front of the whole team.