Mastery criteria sounds less like MAP, and more like end-of-course assessments, or benchmarking assessments for third grade, which could be unit tests out of the curriculum, or achievement testing, or any one of many other instruments. I wouldn't worry too much about prepping him. If you want to know what the criteria are, I would echo indigo, and suggest you read the CC standards or, better yet, take a look at your state's curriculum frameworks document for ELA third and fourth grade.

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