Hong Life CalculatorsUnderstanding the school starting age calculator — concept and principle
This calculator works out when a child starts school, their age on the first day, their current grade and the year they finish school, for South Korea, Japan, England and the United States. Parents use it when planning a move, comparing systems or checking which class a child born late in the year joins.
How it is calculated
- South Korea: elementary school starts on 1 March of the year after the year the child turns 6, so all children born in the same calendar year form one class.
- Japan: school starts in the first April after a child reaches 6; children born 2 April to 1 April of the next year form one class.
- England: Reception starts in the September after the 4th birthday (born 1 September to 31 August form one class).
- United States: most commonly kindergarten at age 5 by 1 September, but each state sets its own rule.
- Current grade = school years since entry; final year = entry year + number of grades.
The principle
Each country fixes a cut-off date: children born after it wait another year. Korea uses the calendar year of birth, which is why a December baby is among the youngest in the class. Japan counts age legally from the day before the birthday, so 1 April birthdays join the older class. After entry, a child moves up one grade each school year, so the current grade and graduation year follow from the start year. Korean and Japanese schools have 6 years of elementary, 3 of middle and 3 of high school.
Worked example
Default inputs: born Dec 2, 2018, South Korea, reference date Nov 10, 2026.
- The child turns 6 in 2024, so school starts Sat, Mar 1, 2025, in elementary school, first grade.
- Age on that day = (Mar 1, 2025 − Dec 2, 2018) ÷ 365.24 = 6.2 years.
- On Nov 10, 2026 the 2026 school year has run since March, so the child is in elementary school, grade 2.
- Compulsory schooling begins Sat, Mar 1, 2025; the last school year ends in 2037.
How to read the result
The dates follow the standard rules; early or delayed entry, repeated years and moves between countries change them. Within the same class, children born early and late in the cut-off year can be almost a year apart in age, which is normal.
Common mistakes
- Using Korean "year age" or lunar age instead of the birth date.
- Assuming one US rule applies in every state.
- Forgetting the Japanese 1 April rule.
- Confusing Reception in England with Year 1.
Frequently asked questions
When does a child born in December 2018 start school in Korea?
On 1 March 2025, in first grade of elementary school.
Why are Korean classes grouped by calendar year?
Entry is fixed to the year after the child turns 6, regardless of birth month.
When do children start school in England?
Most start Reception in the September after their 4th birthday.
Sources: 초·중등교육법 (Elementary and Secondary Education Act), art. 13 and Enforcement Decree art. 44 · GOV.UK, "School admissions: school starting age" · Education Commission of the States, "50-State Comparison: Kindergarten entrance age"