First form = 6th grade (about 11 or 12 years old), second form = 7th grade (12 or 13 years old), etc. So fourth form girls are in 9th grade and are about 14 or 15 years old. Fourth form and upwards = 9th, 10th, 11th, and 12th graders -- high school students, in other words.

What age is fourth form?

Second year, age range 12 - 14. Third year, age range 13 - 15. Fourth year, age range 14 - 16.

What is the fourth form?

fourth form in British English

(fɔːθ fɔːm) education, British. the fourth year of study in a school. He's in the fourth form.