what was told to me during primary is that you are being graded per the FWOP, so if you say EXACTLY what is in the FWOP in the boldface print then AT primary you cant go wrong, all they have to grade you on is the MPTS and the FWOP so say exactly as in the FWOP. Flight school is black and white in the begining.
Key words here are "in the beginning". You get a taste of real world comms on a primary cross country, and get to practice even more in advanced and after wings. The key to primary comms in contacts (FAMS for you old farts) is making it standardized for the sake of learning and brevity. Once you get into later stages, you can start getting "out of the box" and using real world stuff. Even after wings, flying in the big bad real world, the same three steps always apply: Think, key, speak. As long as you are concise and say what you need to, then you are getting the job done. You will (probably) know if you are jacked up.
I always tell my students who are struggling with real-world comms to go to one of those ATC feed websites (atclive, I think) and listen while they are studying.
RE: a previous post pertaining to throwing out "good morning" and such nonsense over the radios:
WTF cares? As long as it is in a non-busy environment, for example with ARTCC or checking in with a non-saturated approach controller, I always find it makes flying a little more enjoyable to exchange greetings with controllers or throwing a "good day" on the end of a handoff. It is kind of like asking for sports scores, it breaks up the freaking monotony sometimes.
Obviously if you are checking in to Tampa Approach during rush hour, you are going to be all business and even then lucky to get a word in. I once got told by Tampa "Last aircraft spoke too fast, try me again in a couple minutes".