I think that the pretest is a good idea if you have time prior to the start of class. However, I think the best way to determine the efficiency of learning and the rate at which the students are learning is to do an evaluation during the course to get feedback from the students to get an understanding of hot to change the course delivery so more learning is accomplished. The only forseeable problem is that some students by the middle of the course have potentially given up on the course. How do you gage when you should reevaluate the course, after two lectures, after five, how do you know when you need to try something else when you only have so many lectures to get the content through. You cannot go back and start again, so what do you do?