More California community college students are taking online courses than a decade ago, but fewer are completing and passing those classes compared with traditional ones, according to a study released Wednesday. Overall, enrollment in online community college courses grew by almost 1 million classes between 2002 and 2012, according to the study, conducted by the nonprofit Public Policy Institute of California. The group studied six years of data, including grades and course enrollment, from the state’s 112 two-year colleges, which make up the largest two-year college system in the country.