"Can I have another piece of pie?" Leroy "Encyclopedia" Brown asks his mother in the first chapter of ENCYCLOPEDIA BROWN, BOY DETECTIVE. Considering her career as an English teacher, she tells him he may have another piece.
The second graders are listening to me read this book aloud, and I stopped here to ask if anyone knew why his mom changes the word from can to may. Most of the hand-raisers had theories, but only one young girl was in-the-know on this one. She explained it well.
"Can means you are able to do it. May means you are allowed to do it." Nodding heads indicated their understanding.