A 9-year-old rock fan up late at a Bruce Springsteen concert had a note for his teacher if he was late for class the next day — and it was signed by The Boss himself.

Fourth-grader Xabi Glovsky and his dad, Scott, attended the sold-out show in Los Angeles on Tuesday and they caught Springsteen's eye with a homemade sign that said: "Bruce, I will be late to school tomorrow. Please sign my note."

After the show, Springsteen invited the pair backstage where they posed for photos. And Bruce scribbled a note for the Claremont boy's teacher.

The note said: "Dear Ms. Jackson, Xabi has been out very late rocking & rolling. Please excuse him if he is tardy."

Springsteen posted the photos and the note on his website, retweeted from Xabi's dad's account.

Scott Glovsky told his hometown newspaper the note came in handy because Xabi woke up at about 10:45 the next morning "with a big smile on his face."

The father is a die-hard fan who has attended dozens of Springsteen concerts in the last three decades. He says he has been singing Xabi to sleep with Springsteen songs since he was born.

"I imagine that idols rarely live up to your expectations. Bruce lived up to every expectation a 9-year-old boy could have — or a 48-year-old boy could have," Glovsky told the Claremont Courier.