1. The state board of education shall adopt a policy relating to the expungement of disciplinary records of pupils who have graduated or reached the age of twenty-one years.
2. Any school district may adopt a policy consistent with the policy adopted pursuant to subsection 1 of this section.
3. No such policy shall allow the expungement of any act listed in subsection 1 of section 167.115 unless the petition regarding the act was dismissed or the pupil has been acquitted or adjudicated not to have committed the act.