I know this sounds counterintuitive, but the research finds that one of the best quick measures of reading comprehension is actually oral reading fluency. It's not a direct measure, but it is a way of indirectly quantifying growth in reading comprehension. I've posted a few ORF charts in the past. Here's another one:

http://www.readnaturally.com/knowledgebase/documents-and-resources/26/386

You can also use some of the resources from this page:

http://www.interventioncentral.org/curriculum-based-measurement-reading-math-assesment-tests

...pronounced like the long vowel and first letter of the alphabet...