From Scarsdale, N.Y., to Bloomfield, Conn., to Lawrenceville, N.J., students are getting hands-on lessons in how to plant vegetables, compost and prune.

• 行知学校的学生虽然身处城市，但是他们和外界的交往并不多，很多孩子来北京多年还没有见过天安门，长城，鸟巢等北京的标志性建筑。