Grosse Pointe (Mich.) Public Schools has received its largest donation--a $500,000 grant from the John and Marlene Boll Foundation; $200,000 of it will be spent on a new pool, gym and fitness center at Grosse Pointe South High School. The center will be named for the Bolls in recognition of their gift toward the $11.6-million project. It hasn't been determined how the remaining $300,000 will be spent.