You started with 50 people, and only 19 made it to the state exam? that's a 60% drop rate..... that's actually a lot higher than I would think, and could be cause for alarm. But in order to cause the alarm, you need to dig deeper, and ask why is the drop rate so high.....
1) are the students not passing the written exams?
2) are the students not passing the in class quizzes?
3) did they decide EMS was not for them?
4) were they unable to put forth the time commitment required for the class?
5) are students not passing the practical exams?
One of my colleagues was taking an EMT class, and wasn't doing very well. His instructor gave him a take home quiz that he needed to turn in the next class. So another EMS instructor and I decided to take a look at the exam. Out of 20 questions, I knew 3 or 4 of them. The rest were so obscure, or not relevant to the EMT class or anywhere near the EMT level, that I saw that the problem wasn't coworker, but the instructor. That instructor (and the program director) have since been replaced), and my colleague retook EMS class through another college.
If you don't understand any of EMT class, yet you are passing all the exams, maybe you simply lack confidence because you lack experience (which is super common by the way). Study guides are great but in the real word, you don't get to use them. If you don't understand A&P, why not take a college level anatomy and physiology class? if the diseases are causing you issues, maybe a pathophysiology class at the local CC would help you
I can respect your desire to be in the medical field, but if you aren't understanding any of it, than the possibility may be that the medical field is not for you.