ACTON — It is 6:30, a time of morning no teenager likes to see firsthand. The sun hasn’t yet risen, and outside, along the sleepy loop of Lexington Drive, snow and sky are twilight gray.
Inside a peach-colored house, two sisters are reluctantly prying themselves from their beds. Downstairs, their father, David Zhou, is frying eggs. Their mother, Jianlin Li, is getting herself ready to drive the school carpool and head to work.