Students from at least one Bay Area high school took part in a nationwide walkout Wednesday dubbed “Stand for the Second,” an effort “to protect our natural rights that are enshrined in the constitution.” About 50 students walked out of class at California High School in San Ramon around 10 a.m., spokeswoman Elizabeth Graswich of the San Ramon Unified School District said. They held signs, made a couple of speeches and returned to class after about 15 minutes, she said.