An important goal for California is that public high schools continue to make progress in closing the achievement gap between demographic groups and that students are prepared for postsecondary education. In early 2008 Commission staff started developing a composite measure of academic preparation based on standardized test scores in nine college preparatory subjects. Proficiency in these subjects is directly linked to the knowledge and skills that students need to acquire to be successful at the university level. Staff decided that a measure comprising multiple dimensions of preparation would be more useful in assessing school progress and success than would an assessment strategy relying on a single subject area. Preliminary results indicate that the Commission's measure correlates slightly better with one-year- and two-year persistence than does the school's Academic Performance Index (API). The Commission's measure has the advantage that it is based on data that is broken down by gender and ethnicity, so it can be used to assess how opportunities to prepare for postsecondary education vary by ethnicity and gender.