Like all people (kids and adults), they have to learn how to take the bumps and how to avoid them. In teaching some highschoolers one of the students knew everything and she kept having to resew seams - I stopped "stopping" her when I saw a problem and just let her fun - she too was upset when it didnt' work out. That lead us to the discussion about what could have prevented it from happening. She eventually got it....then, unfortunately, told her cousins that she'd teach them how to quilt/sew!!!
If you want a site with fun small projects, check out SheCanSew.com lots of free patterns for smaller items.