In the UK, students usually start at the age of 5 and enter the first year of school. Primary school is made up of 6 years. Students then follow on to secondary school, which they end with their GCSE exams. Each subject is assessed seperately by a series of exams leading to GCSEs or international GCSEs. 
Students can then choose to go on to college, where they choose 3 subjects (sometimes 4), which are also assessed seperately and form the basis of entry to university and other courses.
Colleges often also offer other qualifications, leading to students gaining employment and apprenticeships.