I have a class with fifty five students in it. When I use the attendance plugin, it splits them into three pages -- the first two have twenty-five students each, and the third has the remaining five students. I've hunted high and low for a setting change that will show all fifty five on one screen. Does it exist? It used to. A year ago, in a previous version of Moodle, I had a class the same size, and the attendance plugin would show them all on one screen. Now, however, I can't figure out how to get back to that.
Have you tried altering the 'results per page' setting?
Site Administration -> Plugins -> Activity Modules -> Attendance