The chief technology officer of eBay sends his children to a nine-classroom school here. So do employees of Silicon Valley giants like Google, Apple, Yahoo and Hewlett-Packard. But the school’s chief teaching tools are anything but high-tech: pens and paper, knitting needles and, occasionally, mud. Not a computer to be found. No screens at all. They are not allowed in the classroom, and the school even frowns on their use at home. Schools nationwide have rushed to supply their classrooms with computers, and many policy makers say it is foolish to do otherwise. But the contrarian point of view can be found at the epicenter of the tech economy, where some parents and educators have a message: computers and schools don’t mix. This is the Waldorf School of the Peninsula, one of around 160 Waldorf schools in the country that subscribe to a teaching philosophy focused on physical activity and learning through creative, hands-on tasks. Those who endorse this approach say computers inhibit creative thinking, movement, human interaction and attention spans.