Algebra I, Geometry, Algebra II. That’s the usual three-year sequence of high school math courses for students who want to attend one of the 23 campuses in the California State University system. But now that list may grow by one. In a controversial move, the CSU is considering requiring a fourth year of high school math of all freshmen applicants. The extra year-long course could be the traditional calculus or more practical alternatives such as statistics, computer science or personal finance, administrators say. Whatever the courses, advocates say that requiring four years of high school math will make more students ready to tackle mandatory college math courses and improve CSU’s graduation rates. But critics say they fear the possible harmful impact on underprepared students in low-income and high schools already struggling to find enough math teachers. Skeptics say the change could shut the door to the nation’s largest public university system for some students who don’t have access to 12 grade math classes or the skills to complete them. Some form of the plan may be introduced for discussion at the CSU Board of Trustees meeting in May, with a vote possibly scheduled at a future session, officials said. If approved, it likely would not take effect until 2025 or so, to allow school districts and families time to get ready, according to CSU administrators. After all, the CSU’s size is enormous: it enrolls about 428,000 undergraduates, including about 90,000 freshman. Among the plan’s supporters is CSU trustee Christopher J. Steinhauser, who is also superintendent of Long Beach Unified School District. His district already requires four years of math, which can include computer science or statistics courses, for high school graduation. That’s a higher standard than most other California districts.