Noting that anybody under 18 [that is 17 years, 364 days and 23.99999 hours old etc.] is a minor
I would obtain some advice from your local authority EHO's etc and the local education people noting that some of these people may still be in school

This is a hard area to evaluate and adequately manage because your people are in the public domain over which you have very little if any control so when a person [who is a minor] is out on their own they are their own manager

Properly studying the 1800's and early 1900's will show that it is without doubt a lot safer on the city streets in 2011 for an individual working class person than it used to be but in those days ordinary people had almost no access to any form of claim against an employer so the risk has shifted from the person on the street to the person putting them on the street!

All that said undertake a young person risk assessment as required and go from there as people can still walk the streets