Teaching Techniques: In-class quizzes

I have just learned of a very interesting technique used to teach classes.  In this technique, the professor generates a 3-question quiz for the class.  Each question is made in a way to summarize one of the 3 points planned for teaching in that day.  If a large percentage of the class gets it wrong, then the lecture continues until it is finished, when the second question is posed for the second point, and so on.  If a large percentage gets it right, say about 95% or more, then the topic is skipped, and the second question is presented.  If slightly fewer people get it right, say about 85%, then the students have an opportunity to discuss it with each other, and the percentage rises to the 95% level or so, then the lecture for that topic is skipped for the day, because the students obviously understand it well enough already.

Interesting idea.  This was developed by a professor at Harvard.  It seems to work very well in idea.  The question is, how do you get the students to actually read the material beforehand in order to understand the topics and pass the quizzes?