Many schools out there, but real education comes from the teacher so it is always hit or miss whatever school you enroll in. Sea School on the East coast has been around and refined itself over the years like many so again, as long as they are certified by the USCG to give the exam, it may not matter.
You still have to prove sea time and it is reviewed by the USCG as a "reality check" if you were really on the water for the required amount of time, on what vessels, where you did it and probably what you may have learned along the way.
Yes.... the courses prep you for the tests. They also cover all the subject areas you need to know about. ANY professional training never teaches you everything or gives practical experience. No employer assumes a guy with a captain's license in their hand and little or no professional experience is much more than a recreational boater till they prove themselves. I have seen more than a few "licensed captains" get fired because their perception of how good they were was far below what was required for their level of license.
No matter what, to get a job learning anything, good chance that you will need the license first to even get hire. Not many entry level jobs do you get tutored as when working, teaching takes a back seat to getting the job done.
Many of my 6-pack captain graduates worked as mates on sport boats, got their license to run the boat and within a few years had forgotten most of the course material except what was commonly necessary in running that boat. So the system is imperfect, but I saw the same behavior between captains that had taken a "licensing course" or had done it by coming from the deck plates.
Bottom line, the ONLY thing that makes you become a better captain is not licensing or just getting out on the water.......In MY experience the best captains make a list of subjects to learn from a guidebook like a 30-40 year old Chapman's, the research newer concepts and ideas and STUDY, STUDY, STUDY! An alternative guide are subject lists in a licensing course or any source that describes everything from weather to boat handling/navigation to anchoring to....and the list has dozens of subjects. Heck, just TF provides enough info to start that list, just you have to go WAYYYYYYY beyond to cover each subject.
Being on the water is part of the mix, but being out there and not applying what you have learned and then reviewing is just a part of boating (fun part. Also being out there without knowing the thousands of things to know to observe while out there is a missed opportunity.