"Year 7" is not high school in the US. That is distinctly junior/middle school.
Year 7 is also the first year of secondary school (high school) in the UK.
Year 7 is also the first year of secondary school (high school) in the UK.
The thing is, while the US tends to have the Elementary/Middle or Junior High/(Senior) High split in most places, the grade levels aren't the same.
I've seen (and this may not be exhaustive) the splits with the following grade levels:
1-5/6-8/9-12
1-6/7-8/9-12
1-6/7-9/10-12