Are school uniforms necessary?

Yes, Uniforms is required; and the main purpose of school uniforms to create discipline in the life of students. Although some of the schools are creating businesses to increase profits i.e. buy the uniforms from school shops or particular shops fixed by the school management.

And the government school gives school uniforms to needy students free of cost.

I would think so , it instills discipline and also brings in a sense of equality among students ..

I have two children. While my elder one goes to a school with uniform and they had it from KG. My younger goes to a Waldrof school and is in Middle school there. They have no school though they have dress code to be followed. I find pros and cons with both. As a parent I feel that I do not have to do so much hunting for right kind of dress for school and it does save me money when there is uniform. But developmentally making a choice ( of what to wear) is very important and it shapes the individuality of the child. That developmental need goes unfulfilled in case of uniform.

Yes, definitely 

School uniform teaches equality among all students.

I think school uniforms should be long enough in the first place.