(a) Except as provided by Subsection (b), a school district may not schedule the last day of school for students for a school year before May 15.
(b) Notwithstanding Subsection (a), a school district that does not offer each grade level from kindergarten through grade 12 and whose prospective or former students generally attend school in another state for the grade levels the district does not offer may schedule the last day of school on any date permitted under Subsection (a) or the law of the other state.