I think it is necessary for sencondary school students to wear casual clothes when they are at school.
Firstly,wearing casual clothes makes students feel comfortable.Because they don't like to wear school uniforms,it make they feel uncomfortable.
Secondly,wearing casual clothes can gives students freedom of choice.They have rights to choose sizes,colors and fashion,that they love.
Thirdly,wearing casual clothes makes students feel self - confident when they are in their favorite clothes.
Finally,wearing casual clothes make school more colorful and lively.
Therefore,students in all secondary school should wear casual clothes.