Although this one seems stupid, let's pick it apart a bit because there is a huge issue underlying it.
You are a member of the National Guard or the reserves. You do your weekends, you do your time faithfully and then all of a sudden your unit is activated and sent to Iraq, Afghanistan, or maybe even just some assignment stateside that is 2000 miles from home. What happens to your job and employer?
As the employee and National Guard member, your activation will require that you leave your job for a year. You most likely were making more money from your job than you are now making from active duty so you now have a financial hardship. This sounds bad financially.
As the employer, you just lost a valued employee for a year. You are obligated (morally if not legally) to hold his job for him for when he gets back a year from now. Do you still pay his salary while he is gone? Can you afford to pay him his normal salary for the year while he is gone or are your pockets not deep enough. Keep in mind that you will need to use the money you were paying him to hire a replacement for a year. If you do pay him his salary while he is gone and hire a replacement, you are now still getting one person's work but paying two salaries to get it. This sounds bad financially and what do you do with the replacement a year from now.
There are a number of large companies out there that do have complicated policies involving paying the difference in the employee's current salary and his National Guard salary. In these cases, the employee suffers no financial hardship. The company suffers financial hardship but is large enough that they feel they can absorb it. Maybe it means a 2 cent price increase across the product line, maybe not.
Now take a look at the article again and the screwy pay policy it talks about with all the above in mind. He is absent from his employer and not taking paid leave. The school district is still paying his salary minus what the guard is paying him and minus the cost of a substitute. For the school district, it is a zero-sum game with taxpayer money. They are spending the exact same amount of money as they would normally spend for the teacher, it is now just divided up between the teacher and the substitute. The teacher on unpaid leave still actually receives some pay and benefits and it is an amount more than if he just got his National Guard pay and less than his full teacher salary. The thing seems screwy but this particular employee is making out better than many who have been called up.
The root problem here is that there has been a massive call up on the National Guard and reserves that has forced a reevaluation of the many unit classifications that predominately do not exist in the military and that had been moved off to the guard and reserves. We now can't mobilize the military without mobilizing the guard and reserve units because many vital support function units only exist in the guard or reserves.
Senator John Kerry has proposed increasing the size of the military for a decade by 40K troops. 20K of these troops will be in vital support functions that are currently only performed by the National Guard and reserves. The other 20K will be a new army combat division. This would decrease reliance on the National Guard and reserves and reduce the need for massive call ups and hardships.
