mandatory school

Children born between 1 April and 31 August can start the September after they turn 5.
For example, if your child reaches compulsory school age on 31 March, they must start full-time education at the beginning of the next term (summer term that year).

Under “license or permit revocation; reports; investigations,”(Wis. Stat. 115.31), school district administrators are required to report to the state superintendent the name of a person employed by the educational agency who meets the statutorily-defined criteria in Wis. Stat. 115.31.
Districts may use the License Review Referral Form PI-1620 when submitting the report

If you have valid reasons, you can apply to defer or delay your child’s entry into Primary 1 (P1) of a mainstream school, or Junior 1 (J1)/P1 of a government-funded special education (SPED) school. Find out how to apply.
All Singapore Citizens born after 1 January 1996 and living in Singapore must attend a national primary school unless an exemption is granted. Learn more about compulsory education, exemptions and deferment to enter Primary 1.

In the USA, children start school when they are five or six years old. Depending on the state, schooling is compulsory until the age of 16 or 18. Children younger than five can go to a nursery school or preschool.
At the age of five or six, the children attend elementary school (also known as grade school or grammar school), which last six years. The fist year at elementary school is called kindergarten.

References:

http://dpi.wi.gov/licensing/mandatory-school-district-reporting-educator-misconduct
http://beta.moe.gov.sg/primary/compulsory-education/
http://www.ego4u.com/en/read-on/countries/usa/school
http://www.ed.ac.uk/education/undergraduate/degree-programmes/primary-educ