I can see from where you are coming. However, there is nothing really that is free. If it is free, then there is a breech in copyright laws. What you have instead are convenient on-line services. The three most famous are: Netflix, itunes, and Amazon (with prime service). All of these companies offer online movies at a small fee. With Netflix, you will need to sign up for membership. Also you need to keep in mind that these sites may not have the movie that you need to watch. So, the best thing to do is to check out the websites to see if the movies are there.
If you really need to watch something for free, there are two other options. First, Netflix once in a while has one month free memberships. You can sign up for one month and then cancel your membership. Also Amazon offers it prime service free for one month for students with school email addresses. I do not know if this applies to high school students, but it does apply to college students.
The final option is to ask someone with membership to help you out here. Good luck.