In the first four years, I had to cover exactly one class in 728 school days. In the past two weeks, I've had to cover six classes. Typically, coverage only happens if teachers need pulled for a single period (perhaps for an IEP meeting or a post-observation conference) but recently, teachers have been getting period-by-period coverage for the entire day. This means one of three things: the teacher called off sick too late to have a sub called in, there were so many teachers out that there just weren't enough subs to all the openings, or the job was never even posted for subs. In other words, either teachers aren't coming to work, subs aren't coming to work, or there have simply been a rash of early-morning illnesses. None of the answers really makes sense.
More than likely, what we're seeing is the solution to budget issues. Rather than cutting a job, or removing extracurricular programs, this is an easy way to save money by avoiding hiring subs. It's an example of one of those typically unseen deficits that a lack of funding can have on a school. Is it the worst thing? No...because I got out of cafeteria duty, but when the entire teaching staff is filling in for classes on their off periods, and the secretaries are scrambling to find coverages, and the administration has to cover cafeteria duty...it leads to extra stress. Eventually something has to give.