The problem of education

I've been thinking about the problem of the teaching profession in Ireland because of all the teachers union conferences recently.
I'm not going to pretend to understand the full career requirements or motivations of people to choose teaching over another profession; but I think that it is an important area of ambiguity that needs to be addressed.

From my point of view the benefits and positives of being a teacher are:

•     Stable employment once your are taken on full time
•     Opportunity to work with young people
•     Opportunity to shape and direct young adults
•     Able  to focus on a subject that you have some interest in
•     Long holidays
•     Tenure (where you are full time)

The negatives (for me) would be:

•     Putting up with disruptive kids
•     Repetitive nature of the material
•     Lack of direction in terms of career development.

I want to focus on the last one for the moment as its probably the one I know least about.
How does a teacher progress? I assume that you start off on an entry grade and over time maybe you teach higher level classes, or more subjects or become year heads. Maybe the ultimate objective is to become principle or vice principal? (Feel free to enlighten me, I really know nothing about this topic!)

In my line of business I advance by going for roles with more responsibility or I move into roles that I feel can benefit from my experience plus give me knew understanding. In theory I can indefinetly move diagonally upwards. to my mind there is effectively a cap on how much authority you can achieve as a teacher.

How do you get salary rises? If your salary is linked to the number of students you teach, or the number of classes you take then you might be able to cheat the system by offering your services and targetting those classes and subjects that are in demand at that time. However this reflects nothing of your achievements. Good exam grades might be a start but only exam year teachers could be assessed. Non-standardised end of year exams can be easily gamed to produce lots of good results; Cross-marking and exam setting have the same vulnerability. Obviously a class full of A's isn't likely so the bell curve can be used to detect cheating in that way, but in effect it pre-determines performance and therefore remuneration?
If anyone wants to explain to me how the Irish system works!