I did an internship at an engineering company during highschool and they gave me various tasks with pretty minimal guidance.

The one that stuck out the most was downgrading their desktops from Vista to XP. Most of the drivers on the XP disc didn't work on the newer hardware so i was pretty stuck. One of the engineers told me to research slipstreaming drivers, which led me on a 3 day journey to creating custom boot discs & successfully installing XP

Give them work that will challenge them & also serve a business purpose if possible