So in America, we have different types of grades based on school starting at kindergarten for me, but sometimes pre-k. (which means Pre-Kindergarten but we call it pre-k) The grades are kindergarten first-grade(6-7) second-grade(7-8) third-grade(8-9) fourth-grade(9-10) fifth-grade(10-11) (these are all the elementary school grades) sixth-grade(11-12( seventh-grade(12-13) eighth-grade(13-14) (middle school so not quite high school but not elementary school either) ninth grade(14-15) tenth-grade(15-16) eleventh grade(16-17) and twelfth grade.(17-18) (these are highschool grades)
This is based on the month you wore born. So let's say you are switching schools because you moved to America, and you are 11 born in May. You would be put into sixth-grade, but if you wore born any time after September 30th you are put in fifth-grade. This is as far as my knowledge goes about the public school system as I was homeschooled most of my life or in a private school where they just put everybody the same age into the same grade so yah. Hope I was helpful!