As far as age is concerned. Like I said some young students are bumped up to a higher class. Now even if Cam is younger he can study along side the graduation class. The only difference is he will not graduate with his peers, instead he will continue to train. 

Students are taught alchemy's consequences early on. However this exam is considered to be one of A.M.R.O's most dangerous. You cannot place completely incapable infants in such a situation. In the final year at least the students have survival skills, hand to hand combat skills, deductive skills. By now they will be skilled in their fields of hunter, sniffer and silencer. What you need to understand is by now our students are proficient soldiers.

Also as cruel as it is, this test is designed for failure and the mortality rate is high. There is no safety net. The students are thrown to the wolves as such the weak are destroyed and the strong preserver. This is the law of A.M.R.O, they will keep the best of the best and they don't care what opinion you have, if you have one you will be staring at a bullet. 

What I can tell you is, graduation will be scarring and not many will have the luxury of graduating.

Welcome to A.M.R.O, the necessary evil.