Complex sentence: East Lake Academy is an elementary school serving preschool through 8th grade, and the School of St. Mary has campuses serving preschool through 3rd grade (the Primary Grade Center) and 4th through 8th grade (the Upper Grade Center).
Split into simpler sentences: East Lake Academy is an elementary school serving preschool through 8th grade. The other is the School of St. Mary has campuses serving preschool through 3rd grade (the Primary Grade Center) and 4th through 8th grade (the Upper Grade Center).