My wife is a public school teacher, so I've dealt with this as there have been times she's been "docked" for exceeding paid time off.

Each teacher has so many contract days - this is what their pay is based on. My wife does some extra duties so I think hers is like 195 days. I.e. she is expected to work 195 days a year. She is given so many vacation/sick days. These are part of the 195 and thus she can take these days and not lose any money. Even though she only earns 195 days of pay a year, that pay is spread out over 12 months. Because the contract year is, in her system's case, mid August to mid-August, what essentially happens is that on each paycheck during the school year, she is not paid everything she "earned", and some of that earnings are held back to be able to pay her during the times of year school is closed.

That understanding of their pay system is critical.

You take the total salary and divide by number of contact days, and get a daily rate of pay.

If you take a day off without pay, in her school system, the reduction of paycheck comes in the 2nd paycheck after the day in question. For example, if she took an unpaid day off today (Jan 6th), her Jan 15th check would not change, but her Jan 31st check would be reduced. Her gross pay on that check would be reduced by one duty day's pay (or in her case, 1/195th of her annual salary).

It's different, though, if it is extended leave, like for a longer-term illness or maternity leave.

As I said above, the paychecks during the school year are not for the full amount earned each pay period, essentially some is held back in order to pay them when school is closed. So each employee basically has a mini-deferred income-type scenario.

If you are going to be out for a longer-term of unpaid time off, they will continue to issue regular semi-monthly paychecks until all of that "deferred" money is paid out. Once that's out, they stop paying you.

If you return to work before the end of the school year, then they calculate how many "contract days" are left for you, multiply times the daily rate, and that's your "salary" for the rest of the year. They then take that amount, divide by the remaining number of pay periods in the contact year, and that's your gross paycheck for the rest of the year. (when I say year, I mean contract year, not calendar year). If you miss additional days during this time, it's treated as mentioned above for a random day off.