California Code, Education Code - EDC § 51938

(a) A parent or guardian of a pupil has the right to excuse their child from all or part of comprehensive sexual health education, HIV prevention education, and assessments related to that education through a passive consent (“opt-out”) process.  A school district shall not require active parental consent (“opt-in”) for comprehensive sexual health education and HIV prevention education.

(b) At the beginning of each school year, or, for a pupil who enrolls in a school after the beginning of the school year, at the time of that pupil's enrollment, each school district shall notify the parent or guardian of each pupil about instruction in comprehensive sexual health education and HIV prevention education and research on pupil health behaviors and risks planned for the coming year.  The notice shall do all of the following:

(c) Notwithstanding Section 51513, anonymous, voluntary, and confidential research and evaluation tools to measure pupils' health behaviors and risks, including tests, questionnaires, and surveys containing age-appropriate questions about the pupil's attitudes concerning or practices relating to sex, may be administered to any pupil in grades 7 to 12, inclusive.  A parent or guardian has the right to excuse their child from the test, questionnaire, or survey through a passive consent (“opt-out”) process.  A school district shall not require active parental consent (“opt-in”) for these tests, questionnaires, or surveys in grades 7 to 12, inclusive.  Parents or guardians shall be notified in writing that this test, questionnaire, or survey is to be administered, given the opportunity to review the test, questionnaire, or survey if they wish, notified of their right to excuse their child from the test, questionnaire, or survey, and informed that in order to excuse their child they must state their request in writing to the school district.

(d) The use of outside consultants or guest speakers as described in paragraph (2) of subdivision (b) is within the discretion of the school district.