I am the intervention teacher for our district's 5th grade. My directive was to focus on math.
The psychologists at our school told me about AimsWeb as a universal screener for math, and they also had the materials.
Yes, it is easy to administer the probes. They are not necessarily quick to grade. Each digit in the answer must be graded.
Check out http://www.interventioncentral.com
for behavior, reading, AND math RtI information. This is a great site.