State law addresses vision screening.
Colorado Revised Statutes 22-1-116. School children - sight and hearing tests
The sight and hearing of all children in the kindergarten, first, second, third, fifth, seventh, and ninth grades, or children in comparable age groups referred for testing, shall be tested during the school year by the teacher, principal, or other qualified person authorized by the school district.
Guidelines For Vision Screening Programs: Kindergarten Through Grade 12
Guidebook for vision screens
School Health and Wellness State and Federal Legislation and Policy
"C.R.S. 22-1-116: School Children — Sight and Hearing Tests. Mandates vision and hearing screenings in grades K-3, 5, 7, and 9. Parents are notified when a deficiency is found."