http://encounter.arc.nasa.gov/

This is a student program that takes volunteers. They see about 7,000 students and 2,000 adult chaperones each year, giving them each a half-day experience here at Ames.

From their website:

Ames Exploration Encounter (AEE) is a unique educational program designed to inspire positive attitudes about science, math and technology for all students in the 4th through 6th grade (ages 8-14 for summer months.)

Located in a renovated supersonic wind tunnel building at NASA Ames in Mountain View, California; the Ames Exploration Encounter makes math and science curriculum come alive. Students experience science in action and come to realize its connection to their lives.