Thaddeus T. Third III, often referred to as "Chad" or "Ol' Chad", was the man of whom Third Street and subsequent school was named after. He has never been featured in the program Recess in any kind of historical flash back. His statue was featured in the episode "The Biggest Trouble Ever" when it was broken by the gang as the workmen failed to secure it during renovation work.
Presumably, his grandfather and his father before him were also called Thaddeus. We can also deduce that he named his son, Thaddeus. His grandson is Thaddeus T. Third V.