Who said "I should have studied harder."?

This quote is attributed to Charlie Brown.

I should have studied harder. - Charlie Brown

"I should have studied harder."

Charlie Brown Education

"Good grief!"

"I got a rock."

"Rats! I did it again."

"Why is it that everything I do turns into a disaster?"

"Education opens doors."

"Education opens doors to endless possibilities."

"I ain't got the education you got, bub."

"You can't put a price on history."