Complex sentence: The cathedral school at Rochester was founded in 604 AD, at the same time as the cathedral, and was refounded by Henry VIII in 1541 during the English Reformation, when the monastery at Rochester was dissolved.
Split into simpler sentences: The cathedral school in Rochester was founded in 604 AD, at the same time as the cathedral. It was refounded by Henry VIII in 1541 during the English Reformation when the monastery in Rochester was dissolved.