The American school system runs from kindergarten through the 12th grade, which is basically what the K-12 label is. The correlation from age to grade follows basically like this: you start at 5 or 6 for kindergarten, add one grade a year, and then graduate at 18.
The age-to-grade chart
Ages show the typical range during the school year. Every grade spans across two ages because the date of birth can be at anytime through the year.
| Grade | Typical age | School level |
|---|---|---|
| Preschool / Pre-K | 3 to 5 | Early childhood |
| Kindergarten | 5 to 6 | Elementary |
| 1st grade | 6 to 7 | Elementary |
| 2nd grade | 7 to 8 | Elementary |
| 3rd grade | 8 to 9 | Elementary |
| 4th grade | 9 to 10 | Elementary |
| 5th grade | 10 to 11 | Elementary |
| 6th grade | 11 to 12 | Middle school |
| 7th grade | 12 to 13 | Middle school |
| 8th grade | 13 to 14 | Middle school |
| 9th grade (freshman) | 14 to 15 | High school |
| 10th grade (sophomore) | 15 to 16 | High school |
| 11th grade (junior) | 16 to 17 | High school |
| 12th grade (senior) | 17 to 18 | High school |
The level boundaries are different depending on the school district. Elementary commonly runs K-5, middle school 6-8, and high school 9-12, but there are some school districts who run K-6 elementaries, 7-8 junior high school, or K-8 schools that skip middle school entirely.
Why the ranges overlap, and when a child sits outside them
Cutoff dates decide the starting line. A child starts kindergarten in the fall but when do they turn 5? Each state sets a cutoff, usually between August 1 and September 30. A child born in July starts kindergarten having just turned 5 and will be among the youngest person in the grade for each year; a child born in October waits a year and runs older for the grade each year. Our table of kindergarten cutoff dates by state has every state's line that you can check out.
Some families wait a year on purpose. Kindergarten is not mandatory in many states, and families of summer-born children sometimes hold them out a year, a practice called redshirting. Those students then sit a year older than the chart for their entire school career, which is why a high school senior can be 19 years old without flunking.
Retention and acceleration move students the other way. A student who repeats a grade is a year older than the range; a student who skips a grade is younger. Both of these are far less common than the cutoff-date and redshirting effects.
Converting from other countries
Families arriving from abroad hit a bit of a translation problem in more ways than one, because the system in the US doesn't line up with a lot of systems elsewhere. British Year 1 corresponds roughly to American kindergarten, so a UK Year 7 student will be in US sixth grade, one number lower than the label suggests. Most other systems convert cleanly by age rather than by grade name: place the child by the age chart above, then let the school fine-tune it. Schools do this constantly and will place a newly arrived student by age and prior coursework, not by whatever the previous system called the grade.
The school makes the final placement call, and the documents that matter are the birth certificate and prior school records. If the assigned school is not the one you want, open enrollment explains your options for transferring within the public system.
Sources
Grade and age structures reflect standard US public school organization; cutoff dates and level configurations vary by state and district. Confirm placement rules with your local district.
allk12: Kindergarten cutoff dates by state
