Chris Whitehead wore a girls' knee-length skirt to classes at Impington Village College, near Cambridge, Cambs.
He is protesting against a school uniform policy which bans boys from wearing shorts during the summer months.
He also addressed 1,368 pupils at morning assembly wearing the black skirt, which boys are permitted to wear due to a loophole in the policy.
Chris believes that forcing boys to wear long trousers during the sizzling summer months affects concentration and their ability to learn.
He said: ''In the summer girl students are allowed to wear skirts but boys are not allowed to wear shorts.
''We think that this discriminates against boys. I will march in a skirt with other boys waving banners and making a lot of noise.
''I will be wearing the skirt at school all day in protest at the uniform policy and addressing the assembly with the student council, wearing a skirt.''
Teachers at Impington Village College imposed a ban on boys' shorts two years ago following consultation with parents and teachers.ReadMore