Complex sentence: Bremer attended South Division High School, where he briefly started on the school's football team and did well, where he proved to be quite a good player but his mother said he was too ill to play and withdrew him from the team.
Split into simpler sentences: Bremer attended South Division High School, where he briefly started on the school's football team and did well, where he proved to be quite a good player. However, his mother said he was too ill to play and withdrew him from the team.