Fourth year, also known as S4, is the fourth year of schooling in Scottish, Venezuelan, Ecuadorian, Colombian, and other Latin American countries secondary schools, and is roughly equivalent to Year 11 in England and Wales and Year 12 (Fifth Form) in Northern Ireland. In Latin American countries, it is equal to the United States high school's senior year, but the Scottish S4 is equivalent to 10th grade. Most pupils are 15 or 16 years old at the end of S4. It is at the end of this year the pupils complete their Standard Grade or Intermediates examinations. It is also usually the last year of compulsory education in Scotland, depending on what time of the year the pupil was born. Near the end of fourth year pupils pick the subjects they want to take for highers (or A levels as they call it in England). They can also leave school if they are 16.
The term can also refer to the fourth year of a university course.