Are the pages they give us different?

I was told by a girl in my year that you need to write more pages in your essays cus the paper they give you has less space on it.
So say you usually write 5 pages for your comparative in a normal A4 copy, in the exam you should write 6 because the space they give you to write on the pages is smaller.

Is this true? If you wrote about five pages on the exam booklet for an English essay is that acceptable or have I written too little?