When can a boy start working on Merit Badges?

Merit badges can be earned at any time.   Usually, we recommend that new scouts concentrate on the Tenderfoot and Second Class requirements, though, because the skills required for most merit badges are set at 8th grade / early high school level and might be beyond their level of physical and mental maturity.  Good first merit badges for a boy to try include anything that he already has some skill in.   A boy who is a strong swimmer should work on Swimming MB his first summer, for example.  Another good initial merit badge is Family Life MB.  Crafts merit badges are sometimes used during summer camp to introduce boys to the process.