It depends on what the requirements are for the online program you choose. Just like with traditional CNA classes, some educational institutions require a high-school diploma or GED while other do not. In most cases you need to show proof of completing at least a 10th grade education. Check with the school where you plan to enroll and find out their admission criteria. Also, before paying anything, make sure you contact the nurse aide registry for your state and ask them if the program you want to enroll into is approved.