The Salford City stadium has been renamed the Peninsula Stadium after partnering up with Paul Scholes, Gary Neville and Ryan Giggs.
The former Manchester United manager unveiled the plaque and thanked the classmates for their contribution.
Sir Alex Ferguson said he was not surprised the three former players had decided to give something back to the community which gave them such a great start in life.
He said: "A lot of people, including myself, thought you were off your head but none the less putting something back in is the measure of your character."
Salford City now has employment law experts, Peninsula as their main title sponsors while Scholes, Neville and Giggs all own shares in the club.