Cal. Education Code - EDC § 46180. Section 46180.
The minimum day in an opportunity school or opportunity class is 180 minutes. A pupil may be enrolled in an opportunity program for not less than a class period of the school, nor more than 179 minutes per day. Attendance for a pupil enrolled in an opportunity program shall be credited to the regular class attendance.
A pupil who is enrolled in both an opportunity program and a regular school, shall attend school for a period of time not less than the minimum schoolday required for the grade level in which he is enrolled.