Counselors are a common school resource for students navigating complicated and consequential education choices. However, most students have limited access to school counselors. We study one of the largest U.S. policies to increase access to school counselors -- California's Supplemental School Counseling Program. The program increased the average number of counselors per high school by 0.7 and reduced student to counselor ratios by over 150 students. Counselors hired as a result of the program had less experience on average. The expansion of counseling had positive effects on high school graduation and public college enrollment rates as well as on student perceptions of school climate. Impacts on college enrollment were largest in high poverty and rural schools. Thus, expanding access to counselors may help schools address equity gaps in college access and concerns over students' mental health.