It appears that they did this in order to avoid having to rehire teachers based on seniority first:

Teachers begged the School Board to issue layoffs rather than fire them outright because, under the layoff provisions, teachers are recalled based on seniority. There is no guarantee that seniority would be used to bring back any of the fired teachers.

So it looks like there were lots of senior teachers the board wanted to eliminate, not necessarily all of the teachers.

Sure, they are politicizing the process. They don't want to deal with union rules so they fired everyone. It also lets them skip out on benefits, I believe.

But, think to yourself, for all of the amazing teachers they fired, how many just had the wind let out of their sails? I wouldn't come back as enthusiastic about doing the right thing after getting fired like that.

Oh sure, I'm not supporting or criticizing what they did. I was just initially confused as to what a school system was going to do without teachers.

Oh, touche. Should have addressed that. Thanks!