Proposition 74 claims to be "real education reform" by making it easier to get rid of under-performing teachers, currently protected by a tenure system. Some anecdotal evidence suggests that there are such teachers protected by the current system, and that it is very difficult and costly to get rid of them. But according to the California Policy Institute, we simply don't have any data one way or the other to tell us the actual extent of this problem, or of the expected efficacy of changing the tenure system in the ways proposed. In other words, we don't really know how big a problem this is, nor whether this measure does anything to solve it. Given that the benefit of the doubt on any Proposition should always be given toward voting NO, that's one strike against this measure.
On philosophical grounds, I'm generally opposed to tenure as a concept, except in special cases. In general, people should be entitled to keep their job so long as they are performing productively in a valuable capacity, but when they cease to perform well (or their services otherwise cease to be valuable), it's unreasonable to artificially constraint the termination of the employment relationship. That's the way it works for most of us in the "real world", and I see no philosophical reason teachers should be any different. I mentioned that there are certain cases where tenure is justified: a Supreme Court Justice is one example, where the lifetime appointment is important to preserving independence from political pressures. And in university academics, I can see the case for it, where research should be kept free from intimidation against unpopular inquiries. But I don't see any case to be made for public school teachers needing tenure any more than waiters, actors, salesmen or accountants need tenure.
That being said, I think there is a current pragmatic (non-philosophical) justification for public school teachers to have tenure, and that is because tenure as a benefit is a modest form of non-cash compensation to help make up for the fact that teachers are paid less than they ought to be. I would love to see tenure tossed on the scrapheap, and merit pay introduced instead of a rigid seniority system, but coupled with a substantive overall increase in pay across the board. I get this idea from Matt Miller, who has written extensively on this, and has run some numbers and some political surveys to show that this really could work. I highly recommend his book "The 2% Solution: Solving America's Problems in Ways Both Liberals and Conservatives Can Love". You can also find a synopsis of his win-win education reform proposal in this article.
Education reform is desperately needed, and if a more credible and comprehensive solution were put on the ballot, I'd happily vote for it. In the meantime, while I support what they're trying to get at with Prop 74, I don't think I can support this "half measure", which is all stick and no carrot.