Pete plays wonderfully, very believable. Unfortunately, he couldn't save the day. It's not about growing up at SI. It's just a very short period of "his life" when he's 24. He debuted SNL at 20. So chronologically it's not correct. His "sister" is not a sister at all, she's Apatow's daughter. His mother pushed him out of the house when Pete has no place/money to live.
Bottom line: Pete Davidson is 8+, movie - 4.