The Oscar nominee went back to his alma mater in Fort Washington, Pa.

Credit: Courtesy Shan Hill

Lots of people dread going to their 20-year high school reunion. But not Bradley Cooper!

The Hangover star returned to his alma mater, Germantown Academy in Fort Washington, Pa., on Nov. 8 to catch up with friends from the class of 1993 and visit his favorite teachers.

“He has come back to GA a couple of times to talk to students,” a school official tells PEOPLE. “He loves seeing his old teachers and enjoys reminiscing with them. When he says he’s going to do something for the school, he does it. He’s a big supporter and proud to be a part of this school. So it was no surprise that he came to the reunion.”

While his girlfriend, British model Suki Waterhouse was in L.A., Cooper, 38, had a blast reliving the past with his best pal and fellow ’93 classmate Brian Klugman, who stars on the FOX series Bones.

During the reunion, the Oscar nominee – who’s currently shooting a new movie in Hawaii with Rachel McAdams – roamed the halls with his former history teacher Kendall Mattern and toured the school’s new buildings. Later that night, Cooper and Klugman attended the reunion party at MaGerk’s Pub & Grill, where they chatted with friends.

“He was definitely having a great time,” says an onlooker. “He made his rounds and made sure to talk to everyone. He had fun catching up and hearing about their lives. There was lots of laughing and joking going on. He really loved seeing everyone.”

The onlooker adds: “He didn’t act like a movie star. Just a normal guy who was personable and friendly.”

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The following day Cooper and Klugman cheered on the Germantown Academy’s football team against arch rival Penn Charter. After losing for the past 12 straight years, GA rallied past Penn Charter and won. Students joked it was Cooper’s presence that helped break the losing streak.

“He hung out as long as he could at the game. He loved being back at the school,” says a source. “He took his time signing autographs and said hello to a lot of people. He is very modest. I think he has a hard time understanding why people follow him around campus. It’s genuine and not a false modesty. He’s a really good guy.”