Simplify the following text for a Grade 9 native English-speaking person.
Original: The club was founded in 1870 , playing under the Rugby Football Union until 1895 , when they were one of the original twenty-two rugby clubs that formed the Rugby Football League , making them one of the world 's first rugby league teams .
Simplified: The Rugby Union club , Leeds St John 's formed in 1870 , however in 1895 , when many teams broke off to form Rugby League , the club also switched codes .