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.