If all you had to worry about was learning one measure, could you do it well?
By focusing on fewer notes it is easier to get to know them all. And by clearing the field of distractions- in the case of one measure at a time, you are more able to understand everything.
Getting left and right confused is a really common problem for piano students (actually, for people in general).
In this video you will learn a simple exercise that you can teach your students to set them on the path to getting right right. All of the time.
Once you teach it to your students, have them repeat it 20-30 times a day for a few weeks (it only takes 5-10 seconds each time).
I learned it at Alderwood Vision Therapy when my son was having vision therapy for a learning and processing issue.