That would be one route. Another is to go about 50-100 yards west on the access road, make a right into the apartment complex, and go another 200 yards to Wilson.
Or, take the little shopping mall alley directly adjacent to the parking lot (next to the liquor store), drive up to Wilston, make a quick left and then right to get onto Wilson Blvd. Or just head another mile to the entrance to I-66 (by the Metro station).
But that's the point, you're right, there are several egress routes from the school parking lot.