Backed by technology leaders, nonprofits and companies, schools in New York, San Francisco and other cities have committed to offer computer science to students in all grade levels. "In the 21st century, computer science is just as foundational as biology, chemistry," said Hadi Partovi, founder and CEO of Code.org, a Seattle-based national nonprofit that works to expand access to computer science and increase participation by women and minorities. Bringing computer science into the schools ensures that everyone has an opportunity to become digitally literate, said Yasmin Kafai, a professor of learning sciences at the University of Pennsylvania's Graduate School of Education. Jim Taylor, author of "Raising Generation Tech," says there's no evidence at this point that coding or computational learning works or is even needed. Kids don't need to learn how to use digital technology at such a young age either, he added. Computer science doesn't enjoy the benefits of other disciplines, including agreed-upon standards or robust assessments to measure learning, said Jeanne Century, director of Outlier Research & Evaluation at the University of Chicago's Center for Elementary Mathematics and Science Education. In 2015, nearly 49,000 students took the Advanced Placement exam in computer science, a 25 percent increase from the previous year. "Colleges are saying, 'there's an incredible demand, we'd like to see more students become better prepared when they get here'," said Terry Redican, vice president of Advanced Placement program at The College Board. At Marshall Elementary, where more than half the students are low-income, principal Kelly Sheward embraces computer science as an opportunity.