Simplify the following text for a Grade 9 native English-speaking person.
Original: There is some evidence that there has been a school on the site since 1243 but the Harrow School we know today was officially founded by John Lyon under a Royal Charter of Elizabeth I in 1572 .
Simplified: Harrow has educated boys since 1243 but was officially founded by John Lyon under a Royal Charter of Elizabeth I in 1572 .