The children at the Roger Clap Innovation School, an elementary school in Boston’s Dorchester neighborhood, earned quite an end-of-the-year treat. Their principal, Justin Vernon, dressed up as Lady Gaga and milked a cow named Moxie.

What did the children do to earn such august entertainment? They read a lot of books. Vernon had promised them that if they read 10,000 books by the end of the school term, he would dress up as Lady Gaga. They read 13,000 books, and Vernon was true to his word, The Boston Globe reports. He donned a blond wig, black dress and tiara.

“’I can’t tell you how proud of you I am,’ Vernon, dressed as the pop star, told students. ‘And I think I make for a pretty good Lady Gaga,’” the Globe reports.

“Amid the squeals of classmates, fifth-grader Margaret Gould said: ‘We were very excited to see our principal dress up, and we’re really impressed that he did it.’”

The Roger Clap is Boston’s first innovation school. After being threatened with closure in 2010, it reopened as an innovation school in September. The school has about 150 students in pre-kindergarten through fifth grade, according to its website. That comes to an average of about 87 books per student.

Joseph Shea, Boston’s academic superintendent for elementary schools, witnessed the festivities at Roger Clap. “This is absolutely fantastic,” Shea told the Globe. “In my 40-plus years, I’ve never seen anything like it.”