If they were on leave, wouldn't a sub need to be brought in regardless of leave policy? And how is this cheaper than temporary disability insurance where all of the downside risk is shifted to the insurer? That's not a rhetorical question, though I don't expect that anyone will have the answer unless they are a school district HR admin. But it's legitimate question. Is this policy actually in line with the private sector, or is it a perk that the unions managed to swing when times were better that they now refuse to give up?
Also, Jammer is correct. Sick time is rarely accruable. It's a use-it-or-lose-it proposition. Which is why it is so often abused. Which is why my company and many others have simply switched to paid time off (PTO). You get about 3/4 the same amount as you did with sick leave and vacation time, but you take what you take when you want. No need to make employees lie about it. A good policy.
As for piling on public employers, I agree that it is pretty common these days. But I don't think that it is entirely unjustified when you look at municipal, state, and federal budgets. As a taxpayer, I am asked to take a portion of my hard-earned income and give it to the government at various levels. I have every right to question how that is being used and to have a say in it. I may not be able to influence national foreign policy, but I can object when my local school district is paying for five administrators at a single high school at a cost of between $150,000 and $200,000 per year (no, administrators are no unionized). Public employees are an easy target because they are a visible target. I can't be angry with amorphous government programs (well, I can, but it's a bit different). I can be angry with my asshole neighbor who makes $50,000 per year for a part time job calling roll at aldermanic meetings. They are also working folks like you and I. So I want to make sure that I am not being asked to give more of my personal income so that somebody else can enjoy a benefit that I can no longer afford because of my high tax burden.
Sure, there are a lot of other places to look, and union cuts usually hurt the people on the low end of the totem pole--those that can least afford it and have the smallest impact on the budget. We could talk about that. But this was a thread about Wisconsin and public employees' unions. Just because there are worse offenders out there doesn't mean that we shouldn't talk about it. Yes, it's political theater. That doesn't make the premise false. Just the motives.
I think that the solution is very simple. Compare the union salaries, benefits, and policies to those of the private sector. Account for discrepancies in pay. If they are on equal footing, move along. Nothing to see here. If there are gross variances, those should be addressed.