We report our experience in bringing science into US and French classrooms. We participated in the US scientific educational program Project ASTRO. It is based on a partnership between a school teacher and an astronomer. They together design and realize simple and interesting scientific activities for the children to learn and enjoy science. We present four hands-on activities we realized in a 4th-grade class (10 yr-old kids) in Tucson (USA) in 2002-2003. Among the covered topics were: the Solar System, the Sun (helioseismology) and the Galaxies. We also present a similar experience done in two classrooms in 2005, in Chatenay-Malabry (France) in partnership with an amateur astronomy association (Aphelie). This is a pleasant and rewarding activity, extremely well appreciated by the children and the school teachers. It furthermore promotes already at a young age the excitement of science, and provides concrete examples of the scientific methodology.