Are the problems too close together? Make sure you can distinguish between the problem number and the actual problems. The problem numbers should be less obtrusive. Students with and without ADD and ADHD can become distracted by too many distractions!?
Whereís the answer sheet? Are the answers correct? Are the answers listed in a column that you have to match with the student worksheets or on a replica of the student page laced with answers? Last thing you need is to be in a hurry and red mark student worksheets...when their answers were correct all along.