Fyi: it’s called post secondary because, I think, UK calls it primary, secondary, and after that is post secondary.
US.
Middle School and Jr. High vary depending on how the grades break.
When I was coming up it was this:
Grade School: 1-6
Jr. High - 7-9
High School - 10-12
But when I hit 9th grade, they changed it:
Grade School: 1-5
Middle School: 6-8
High School: 9-12