Do your policies describe what youth can and cannot do while doing volunteer construction-related jobs? Resources you can draw upon:

• ACA standard SF-8.Power Tools: Must be used only by trained persons, safety devices intact, in good repair.
• Your state child labor laws
• Youth & Labor, Hazardous Jobs
  http://www.dol.gov/dol/topic/youthlabor/hazardousjobs.htm
• etc.

One example: https://www.habitatsusq.org/volunteer/youth-volunteer-policies