By default "student can re-take" option of Lesson is "No", but its help file says "Yes" on the following description.
- /lang/en_utf8/help/lesson/retake.html
<p>By default this option is <b>Yes</b>, meaning that students are allowed to re-take the lesson. It is expected that only in exceptional circumstances will this option be set to <b>No</b>.</p>