One reason there is relatively high absenteeism at Central Falls High, combined with people going on long-term medical leave or just resigning abruptly, is the unique nature of the district. There's only one high school, you can't transfer out, you're stuck there unless you can get a job in another district. Apparently a few people were able to pull that off, which is amazing considering the job market. If CFHS was in Providence, the worst case scenario would be that you were booted out of your job in a reconstitution and ended up in the sub pool making the same salary with fewer responsibilities and a fresh environment.
Basically, if you trap people in a stressful situation, some will crack, and in this case, crack at the beginning of the school year. Your job as an administrator is to understand the local conditions, anticipate and prevent that kind of situation.
Unless you prefer management strategies which ignore human behavior.