I love using Manila folders to make student art portfolios in my class. They are durable and easy to decorate on. If my students make a mistake they can easily erase and start offer. If they make a huge mistake they can flip them inside out! My students put nine weeks worth of artwork paintings and graphic organizers in the portfolio. I write their scores on the inside cover. This is a great place to do this because my pen does not show through to the other side. I even have had students bring their portfolio back every year do they can see if their work is getting better as they get older.
I use these folders in an elementary school library as the children's library cards and shelf markers. A shelf marker is what the students use to mark their place on the book shelf while they peruse the book to see if they want to read it to make sure it's a good fit to ask the teacher if they may check it out. So they are carried all around the school; they are pushed onto the shelves between books; they are scanned; they get a real workout! But I am still using some from last year. They last and last.