Middle school should be 4 years and high school should be 3 years

I think that 9th grade should be moved from high school to middle school because 9th grade often repeats 8th grade material under the assumption most students are new to high school and aren’t ready for the next level. High school could more focused on college prep for 10-12 graders and moving 9th grade better matches their avg development stage.

Edit: i live in the usa and it seems to be there is many different systems in the usa and in the world when it comes to this i was talking about the elementary 1-5 Middle 6-8 and high 9-12 system