There are after-school events, too, like the one in Mill Valley, where 70 parents and 90 children, ranging from kindergartners to fifth-graders, huddled over computers solving animated puzzles to learn the basics of computer logic.
It is a stark change for computer science, which for decades was equated with trade classes like wood shop. But smartphones and apps are ubiquitous now, and engineering careers are hot. To many parents - particularly ones here in the heart of the technology corridor - coding looks less like an extracurricular activity and more like a basic life skill, one that might someday lead to a great job or even instant riches.
The spread of coding instruction, while still nascent, is "unprecedented - there's never been a move this fast in education," said Elliot Soloway, a professor of education and computer science at the University of Michigan. He sees it as very positive, potentially inspiring students to develop a new passion, perhaps the way that teaching frog dissection may inspire future surgeons and biologists.
But the momentum for early coding comes with caveats, too. It is not clear that teaching basic computer science in grade school will beget future jobs or foster broader creativity and logical thinking, as some champions of the movement project. And particularly for younger children, Soloway said, the activity is more like a video game - better than simulated gunplay, but not likely to impart actual programming skills.
Some educators worry about the industry's heavy role: Major tech companies and their founders, including Bill Gates and Facebook's Mark Zuckerberg, have put up about $10 million for Code.org. The organization pays to train high school teachers to offer more advanced curriculums, and, for younger students, it has developed a coding curriculum that marries basic instruction with video games involving Angry Birds and hungry zombies.
The lessons do not involve traditional computer language. Rather, they use simple word commands - like "move forward" or "turn right" - that children can click on and move around to, say, direct an Angry Bird to capture a pig.
Across the country, districts are signing up piecemeal. Chicago's public school system hopes to have computer science as a graduation requirement at all of its 187 high schools in five years, and to have the instruction in 25 percent of other schools. New York City public schools are training 60 teachers for classes this fall in 40 high schools, in part to prepare students for college.
"There's a big demand for these skills in both the tech sector and across all sectors," said Britt Neuhaus, the director of special projects at the office of innovation for New York City schools. The city plans to expand the training for 2015 and is considering moving it into middle schools.
The movement comes with no shortage of "we're changing the world" marketing fervor from Silicon Valley.
"This is strategically significant for the economy of the United States," said John Pearce, a technology entrepreneur.
He and another entrepreneur, Jeff Leane, have started a nonprofit, MV Gate, to bring youth and family coding courses developed by Code.org to Mill Valley, an affluent suburb across the Golden Gate Bridge from San Francisco.
Parents love the idea of giving children something to do with computers that they see as productive, Pearce said.
"We have any number of parents who say, 'I can't take my kid playing one more hour of video games,'" he said. But if the children are exploring coding, the parents tell him, "'I can live with that all night long.'"
The concept has caught on with James Meezan, a second-grader. He attended one of the first "Hour of Code" events sponsored by MV Gate in December with his mother, Karen Meezan, the local PTA president and a former tech-industry executive who now runs a real estate company. She is among the enthusiastic supporters of the coding courses, along with several local principals.
Her son, she said, does well in school but had not quite found his special interest and was "not the fastest runner on the playground." But he loves programming and spends at least an hour a week at CodeKids, after-school programs organized by MV Gate and held at three of Mill Valley's five elementary schools.