"I decided that I really owe the school a debt for tolerating me this long, so I decided that I better do something to mark it," he told The Early Edition's Rick Cluff.
Charlton said the school's principal, Roger DesLauriers, told him the school desperately needed a new school bus.
"A bus of course is $105,000, which is well beyond anything I was going to raise, but as of last night, I've been able to raise $32,000 and hoping for more," he said.
Charlton's friends have offered to walk with him, but he's told them he's going it alone.
"I kept saying where were you when I was doing the practice walks, I can do this alone," he said.
Charlton has been teaching at Notre Dame for so long that he will watch a former student — who is now the school's vice principal — retire this year after a 35 year career. Charlton plans to keep teaching.
"Notre Dame has become my family and as such I feel very grateful that I've been able to stay there."
To hear the full interview with Alan Charlton, click the audio labelled: Teacher Alan Charlton celebrates 80th birthday with fundraiser.