For most people and for most situations, Unions are inappropriate and destructive.
Think about it: An employment contract is one of the most important agreements in one's life. I agree to do some work, and another person or entity agrees to compensate me for it. If the compensation is unacceptable, I don't agree. If my work is found to be unacceptable, the other party can terminate the contract. If I find that my work is worth more than my compensation, I can bargain for better compensation, or take my services elsewhere, so that I can receive what I am worth. 90% (roughly) of the people in the private sector live their work lives according to these simple rules.
By introducing a Union into this scenario, a number of insidious factors come into play. It is not MY work that determines may compensation, but the value of EVERYONE's work, from the best to the worst. The best workers are discouraged from performing to their potential, because there is no advantage to doing so. The worst workers find ways of doing as little as possible (and sometimes even sabotaging the work), because they know that they are very unlikely to see any ramifications for their laziness. Personal advancement is discouraged because "standing out" is socially unacceptable in the union community.
Government employment is a lot like Union employment to start with, but then, when you formally adopt collective bargaining along with the "right" to strike, it becomes near evil. In true collective bargaining, both sides must be reasonable. If the Union demands (and gets) too much, the viability of the enterprise is threatened, and everybody loses. When a government union demands too much, management representatives are incentivized to make a good showing of "hard bargaining," but there is never any threat to the enterprise if the contract unreasonably favors the Union, so the end result is a gradual inflation of Union compensation to a level that has no rational relationship to what is being "produced" bye the Union members.
In our public dialog, one thing seldom mentioned is the outrageous generosity of the pensions. The reason it "flies under the radar" is that the outrage is not the monthly or annual AMOUNT of the pensions, it is the DURATION of them. Many government employees (especially teachers) are able to RETIRE in their EARLY 50's! This is insane! They will be, on average, on the public dole for 30 or more years while producing nothing! So when we talk about "low" teacher salaries, remember that their full compensation is more than twice that annual amount, because they will be on the pension-dole for AS LONG AS THEIR WORKING LIVES.
Anyone reading this who goes on cruises will note how many of your fellow cruisers are retired teachers. There are a couple reasons for this: (a) they make a good retirement income, and (b) they are healthy are retired for two or three times as long as their private sector counterparts who retire at a normal 65 or 66. For most people, the time to "have fun" is 8-10 years between retirement and, say 75, at which time activities are significantly curtailed due to the normal ravages of age. But if you retire at 53 (normal for a teacher), you have over 20 years of. healthy, well compensated retirement before you have to significantly slow down.