WARWICK HALL looked more like an old English castle than a modern boarding-school for girls. Gazing at its high towers and massive portal, one almost expected to see some velvet-clad page or lady-in-waiting come down the many flights of marble steps leading between stately terraces to the river. Even a knight with a gerfalcon on his wrist would not have seemed out of place, and if a slow-going barge had trailed by between the willow-fringed banks of the Potomac, it would have seemed more in keeping with the