A formidable two-story brick house stands in Georgetown; its exterior gives no hints as to what awaits inside. Once a school for boys in the 1840s, the historic home located at 3014 P St. NW was completely renovated and given over to 15 area interior designers to create the 2008 DC Design House, benefiting the Children’s National Medical Center. The interior is a showcase of sophisticated design, style and luxury; perfect for the neighborhood. Purchased…