Math Reasoning Inventory which helps teachers to formatively discover what students know and are able to do mathematically. From what I can see on the site, they currently offering questions geared toward whole numbers, decimals and fractions which seem to be difficult concepts for students in middle school to grasp. The Math Reasoning Inventory is made up of written expression as well as interview questions. Once completed the website will generate reports at your discretion which can be used to monitor progress or submit to your SRBI team for data collection.
Many schools are already using some form of standardized testing to track student progress but if you are not this could be a great start for your teachers. Even those who are using those tests might be interested in the anecdotal evidence that is derived from the interview questions. I could see this being a teacher goal for middle school math teachers who are looking to enhance data collection in order to facilitate higher achievement.