Socrative is a free web-based testing/quiz site. Students don't need a login name or password, just a room number that is automatically created for you when you sign in. There are multiple options for giving the quizzes and multiple report options for the teacher. Socrative offers real-time grading so you can use it during a lecture to see if your students understand the material or not. Or use it as a quiz tool to have the students become comfortable taking assessments on a computer before they take the CAT/SBAC.
Teacher login: http://b.socrative.com/login/teacher/
Student login: http://b.socrative.com/login/student/