I believe what you have read means the usual, that they will eat Snails(especially Stomatella), Hermits, Peppermint Shrimp, Cleaner Shrimp and similar inverts. Since they prey on animals commonly out of direct sight of the hobbyist, there is little chance for the hobbyist to train the Puffer to stay away from those tasty morsels.
In my experience, when that information is relayed to the kids they will understand and follow your lead, if your wish is in protecting those very useful reef inhabitants from falling prey and leaving the tank vulnerable to nuisance algae, Aiptasia, parasites and other issues.
That's my 2 cents.
Aloha,
Mark