Prepdog.org 6th Grade
Prepdog.org- Prepdog.com is a website with printable quizzes for math, reading, language, and science. They come in different levels, and the website also has tutorials and lessons too. There is a store link, but most of the resources are FREE. It's definitely worth checking out.
NC Mathematics - Elementary
This math instructional site from North Carolina is FULL of links that correlate to the Common Core. All links are by grade level through fifth grade. Click on your grade level and get the standards, instructional resources and more. This is a good one to keep on hand!