Learning went both ways at Williams College’s Summer Science Lab this month. “One of my interns said this morning, ‘The kids were my teachers this week as well,’ ” lab director Stephen Bechtel said last week. Bechtel spoke as week one came to an end at the day camp for rising fifth- and sixth-grade students. The program saw a bump in participation this summer, reaching its capacity of 36 children per week. Those children explored scientific themes and did experiments under the direction of Williams professors Chip Lovett and David Richardson, who are assisted by 18 college interns from Williams and Massachusetts College of Liberal Arts.