"Is this the way all schools teach pre-flights?"
I obviously can't comment on all schools but, based purely upon my own experience (fixed-wing and helicopters), what Sneetch describes is what the vast majority do.
"I have mentioned this to various instructors and other students but nobody seems to be concerned."
They are wrong; you are right to be concerned.
"Am I being paranoid?"
No, not in my view.
There are some exeptions (and I've been fortunate to find some over the years) but, generally, far too little importance is attached to teaching a proper pre-flight check.
Too many instructors tend to cover this aspect in the early lessons and then simply send the student out with a Check List saying 'Do the pre-flight checks and strap in. I'll join you in a minute." Some instructors do their own pre-flight (or walk-round) when they arrive; some don't. Later, when the student knows the start procedure, it becomes 'I'll come out when you've started.'
The result is that there is no means of ensuring that the student has actually learned how to do a proper pre-flight or, as Sneetch frankly admits, even understands what he's looking at or should be looking for.
I suppose it might be argued that the student is allowed to build confidence by doing the checks on his own, but I think in most cases that's just an excuse for the instructor to use the time to take a break.
The more conscientious instructors watch students doing checks, and every few lessons make them call out what they're doing, what they're looking for and why - but, in my experience of fixed-wing and helicopter training, they're the exception.
Tees' suggestion is a good one. But you should also speak to your instructor and say what you've said here. There's no need to be embarrassed. Admit that you're concerned about this aspect. Ask the instructor to do your checks with you and to test you from time to time. If he's any good, he won't mind and will adapt to your wishes. If he doesn't, find youself a better instructor or a better school - it may literally save your life one day.