Simplify the following text for a Grade 10 native English-speaking person.
Original: Notts County are considered to be one of the pioneers of the modern game and are the oldest of the world 's professional association football clubs ( there are older professional clubs in other codes of football , and Sheffield F.C. , an amateur club founded in 1857 , are the oldest club now playing association football ) .
Simplified: Notts County is the oldest of the world 's professional association football clubs ( There are older professional clubs in other codes of football . )