In the USA, kids start school at about age 5 or 6. Depending on the school system a kid can go to elementary school for 6 years, middle school for 3 years, and high school for 4 years; or elementary school for 7 years, middle school for 2 years, and high school for 4 years. In some places middle school is called junior high school.

There are also public schools and private schools. Public schools are payed for with government money and are open to the public. Private schools are more upscale and parents have to pay for their kids to go there. Kids in private schools usually have to wear uniforms and kids in public schools don't.

My explination was breif, but I hope it helped.