Our high school has a person in the Counseling Center who arranges Internships as well as vocational education. Interns work in a variety of settings from hospitals and veterinary offices to stores, preschools, and the local aquarium. Local businesses can ask to be included. The list for this year isn't out yet, but I'll try to remember to link to it once it appears.
I think a lot will depend on the area your main character lives in, what the values are, and what types of business are available. Also, some places can't take on even volunteers below a certain age. For example, you must be 16 or go with an adult to volunteer with animals here. You might do a Google search on high school interns and see what comes up. I often find gems in the fluff of Google when I research things.