Complex sentence: Mrs Kaplan is Headmistress of the Senior School (Grades 8-12) who wear a blazer, white shirt, tartan skirt, white socks and black school shoes.
Split into simpler sentences: Mrs Kaplan is Headmistress of the Senior School (Grades 8-12). These grades wear a blazer, white shirt, tartan skirt, white socks and black school shoes.