What age are kids in ‘pre-k’? I’m imagining like 3-4 years old? I wouldn’t be surprised at that working with some kids that age. Not saying I think the story is true necessarily, but just that young kids are very trusting, don’t always put together information they get in different settings, and don’t really discuss weekend plans with each other much.
A lot of old hard rock and metal with power chords is easy to play a simplified version of. I think Metallica - ‘For whom the bell tolls’ and ‘Enter Sandman’ were probably the first things I learnt. You can learn enough to have fun playing a riff like that even if you struggle to get your hand into position to do proper 6-string chords.