Twelfth grade or Senior year, or Grade Twelve, are the North American names for the final year of secondary school. In most countries students then graduate at age 17 or 18. In some countries, there is a thirteenth grade, while other countries do not have a 12th grade/year at all. Twelfth grade is typically the last and senior year of high school.

In Australia, the twelfth grade is referred to as Year 12. In New South Wales, students are usually 16 or 17 years old when they enter Year 12. All students in Year 12 work towards getting an ATAR (Australian Tertiary Admission Rank) or OP (Overall Position, which applies only to students in the state of Queensland), which will allow them access to courses at university. In Victoria, this is achieved by completing the VCE and in New South Wales this is achieved by completing the HSC.

In New South Wales, when completing the [HSC], students are required to satisfactorily complete at least 10 units of study in ATAR courses which must include:

Students can leave school at the age of 15 only if they have a full-time job or are doing a TAFE course.