I noticed everyone is giving you kind of a hard time on here, but let me intervene.
The idea was great, you had some good sequences in there. Also you had good ideas, (nice use of the ending screen haha). There is just some things you need to work on. One thing I learned is to never have too much black, you need to have footage take up the screen more than black color boards, that way the viewer doesn't get bored. Also, take a look at some cinematic trailer and what not, and one thing you will notice that they are generally short, and mainly surround the entire work, not just every piece. I think a trailer introducing each SCP is good, but I do think they need to be a bit shorter and some refining is required. Other than that you did good. I was 9 years old when I started doing film, and now 8-9 years later I am still with it, and the thing is that everyone seems to forget is the we all start somewhere. Good job kid, keep doing what your doing, you stick with it, and it'll get you somewhere. Don't let other people get you down ok? You just gotta go through with a shield, take in constructive criticism, and always keep an open mind to things. Hell, if you need me to show any thing or give you ideas just PM me anytime, I will be glad to help

Creator of SCP: Containment Breach Trailers, Creator of Containment Breach: Run.
http://www.gageallen.com