SWE sponsors a number of K-12 outreach programs, including:
Exploring New Worlds - SWE's annual signature event, usually held in May. The event brings over 250 local elementary school students to campus for a day of engineering workshops and competition.
Middle School Outreach - A series of off-campus workshops held at local middle schools (usually in East Palo Alto) each year (usually during Winter & Spring quarters). The workshops are prefaced by a short introduction to a fundamental engineering/science concept, followed by an activity that applies the concept.
Junior Engineering Technical Society (JETS) competitions called Tests of Engineering, Aptitude, Mathematics and Science (TEAMS) - Stanford JETS Day brings 100+ high school students annually from all over Northern California to participate in the TEAMS competition.
More information about these activities can be found at http://swe.stanford.edu/cgi-bin/events.php.