Why does it take so long for a rented movie to download?

I rented a movie on iTunes and began downloading. It is not in HD, and all updates have been made to my iPad. It has been 4.5 so far, and it has downloaded 1.1 of 1.5 GB of the movie. This has been going non-stop and has not moved very fast, obviuolsy. I am using my school (public) WiFi for this movie. I have also downloaded a couple of different times using my home wireless router, and it is no faster. When I read online the suggested times it will take to download, the slowest is 2 hours.... Any thoughts??