In the late 20th century, I received a thorough mocking for only putting one space after my periods. “Everyone puts two spaces after a sentence, don’t you know that?” I switched, and have been using two spaces for over a decade.
I have a very heavily-ingrained habit to undo:
I’m working on a book right now, and the publisher is going to expect single spaces after each and every sentence. Even if I take corrective action now, some are still going to slip in, and it’s going to be very time-consuming and error-prone to track them down.
Do your kids a favor, and ensure they’re being taught the single-space style.