I have been in education for 16 years and I belong to a teacher's union. While I appreciate many things a union does for me, I think it keeps bad teachers employed and, as mentioned above, ends up hurting students in the long run. If anything, the union evens the playing field so all teachers are treated the same, meaning teachers I have worked with who are basically jokes in the classroom, do absolutely nothing extra-curricularly in the school get the exact pay as I do (I coach football then basketball, am at the school helping for every tournament, etc.). It is frustrating, to say the least.
Unionized or not, there has to be a level of competence met, but it is virtually impossible to get a teacher fired in our District. I know Geno will say my opinion doesn't matter because I am Canadian (an argument that has long grown old), but truth is, it is an issue that transcends borders. We are falling behind...quickly...and doing things the same old way just doesn't cut it anymore.
If anything, the teaching profession should be under closer scrutiny than many professions because it correlates directly to our future.