My iPad has a white screen with a faint black edge

I have a ipad 4th Generation 16gb which is almost 3 years old. Over the past few months it has had purple, green and white stripes appear occasionally. Slightly twisting the iPad would fix this problem. Recently the screen went white around the edges and now it is white with a faint black edge. Pressing and holding the home and on/off button doesn't do anything. Please help as this is my sons iPad that he requires for school.