That was the question in 1999 when George Stevens Academy and Maine Maritime Academy took a chance and organized the first Downeast Invitational Regatta for high school sailors. Seventeen years later, the party is still going on, and the sailors are still coming from all over New England. Last weekend, teams from 16 high school and community sailing programs descended on Castine for two days of dinghy racing that MMA sailing coach and Principal Race Officer Charles Barclay called “remarkably tight.”