Most free websites will not provide current, peer reviewed research studies. However, there are great primary sources, especially educational statistics, available, as well as many non-profit/ policy/ think-tank papers. Generally, you should use library databases to find your articles, and the web to supplement your arguments with statistics, demographic information, and reports.
Things to keep in mind when searching the web:
You can limit your google search to a particular domain name by entering your search terms followed by a colon and the domain ex. substance abuse:.gov