Don't let them think, for a minute, that you aren't sure what do to about anything. Be aware, too, that they are very good at manipulating those who will let them. This is a generalisation, by the way. There are as many 'good' young offenders as there are bad ones, but in the beginning you can't afford to take the risk.
On the other hand, give them the respect you'd give to anyone you didn't know, ie. be polite and don't keep reminding them why they're there (unless you're, say, a probation officer, in which case I guess you'd have to).