Great way of using Lessons. I would like to invite you try out IntelliBoard. We have report called Lesson Answers which pretty much does what you are looking for. We offer great number of reports and options to make Moodle even more attractive.
Feel free to use our demo site to try it out at demo.intelliboard.net or sign up for free trial at www.intelliboard.net.
We offer reports and analytics for Moodle and we are official Moodle integrator. By using our services you are actually contributing back to Moodle as well. We will be happy to setup time to show our product.