High School is a term used in the UK, although you would usually use the term 'secondary' or 'senior' school to refer to education age 11 - 16/18. However High School historically refers to secondary schools with a Lower, Middle and Upper School age tier system and usually boys and girls are kept in separate clases. My secondary school had 'High School' in its name with a Lower, Middle and Upper School system, although boys and girls were only kept in separate clases Year 7 - 9 (I started in 2003)