“Rossi said his wife formally notified their school of the kids’ absence by email shortly before they left.”
Even when I went to school 50 years ago, if a parent wanted to take a child out for a few days they made advance agreements concerning how to make-up missed classes.
Not enough detail here but sounds like he just notified them and took off.
But...from the article:
"The school has known unofficially about it since the fall. The teachers have discussed it, so it hasn't been a secret."