Tutor or (preferably) after school class in Mandarin

English literate 6 year old has has a year of Mandarin and would like to continue.

Prefer weekend or evening classes with other students, but can work after school or weekends with a tutor.

May be able to provide a location near Dupont Circle (3 blocks from METRO) to hold a scheduled class (max 5) in a large private home.