Bichon frise, maltese, or pug?

I am going to start high school next year and am thinking about getting a dog. I live in a house with a medium sized backyard, and have no experience owning a dog. I am looking for a low maintenence, calm and affectionate lap dog. The dog will need to be left alone for about six hours a day. I have done some research and am thinking about a bichon frise, maltese, or a pug. Can you please give me some insight on which dog will fit my needs the best?
Thank you