On assessment days, I like to go over the study guide with the students to eliminate any last minute misconceptions. Depending on the length of the assessment, I may have students show work on the board or give them the answers and go over any questions they may have.
Our tests are district created, but follow directly with the common core strand for number sense: dealing with fractions and decimals.
Students work independently on the test. As students are taking the exam, I walk around to make sure students are using their learned strategies and taking the test seriously. I will read a question to a student, but will not help them with any problems.
I always provide the students with a quiet activity to do after the test. These activities range from logic puzzles to sukoku's to finding the hidden meaning. Although not directly math related, they do provide the students time to critically think.