The 66-year-old rocker penned the letter for Xabi Glovsky who stayed up to watch the star's three-and-a-half hour show in Los Angeles on Tuesday and explained to teachers the kid had "been out very late rocking and rolling", reported NME magazine.
The boy's father Scott took to social media site Twitter to share the note carefully scribed on white paper and which included the "Born To Run" hitmaker's familiar signature at the bottom.
It read: "Xabi has been out very late rocking + rolling. Please excuse him if he is tardy."
Xabi's father was delighted his idol had taken the time to create the "beautiful" letter and praised the star on his penmanship.