According to USA Today, NYC is no longer taking applications for substitute teachers (hat tip: Gotham Schools). It's unclear exactly why this is, but the blurb on the increase in applications makes it sound like too many people have applied and that they no longer need more subs.
This means one of two things:
1.) Times have drastically changed since my teaching days, or
2.) Somebody is really stupid
Back when I was teaching, subs were a precious commodity at my school -- they were few and far between. One of the dirty little secrets that people outside of schools don't realize is that when subs are missing that "emergency coverages" become common (in elementary schools they often prefer to split classes up and assign a handful of students to other classes for the day).
Since we almost never had subs available, it meant that other teachers had to cover whenever one was absent. When you walked in the door in the morning there was a white slip declaring that there was an emergency and you were needed to cover another class. I usually had 2-3 per week. I used to dread the sight of that little white slip folded over my time card -- the worst was when I had already breathed a sigh of relief only to have a student sent to my room with a coverage slip during homeroom (if not later).
Coverages were one of the worst parts of an awful job. When I first found out that we had to cover other classes during our free periods, it was from a memo distributed to teachers. According to at least one administrator in the building, teachers were supposed to be prepared to teach any other class at any other time in case of a coverage. Did they really expect me to come up with a lesson for Spanish or 8th grade math or choir at the drop of a hat? I asked a veteran teacher if this was how things actually worked. "If nobody gets hurt, you've had a successful coverage" is what I was told. Indeed, I don't think that statement was overly hyperbolic.
In theory, teachers from the same school would better control students than would subs -- but that assumes that students know (and care) who the teacher is. Given the size of the school, most classes I covered didn't know me other than possibly seeing me around the hall. They could've cared less (and wouldn't have known the difference anyway) whether I was the sixth grade teacher from the 3rd floor or some poor sap off the street.
One of the best coverages I ever had was when I covered a chorus class. At that point in the year two chorus teachers had already quit, so the kids were wondering when a new one would come (nobody ever did). I walked into the classroom and the students immediately asked if I was the new chorus teacher. There was only one right answer -- yes, I was, and we needed to get to work right away. I passed out the stack of textbooks that were sitting on the shelves and tried to remember what I'd learned in middle school band. It bought me a solid half hour of relative cooperativeness.
But back to point #2. If there still aren't enough subs to go around, but they've stopped taking applications, then somebody is an idiot. Not only do coverages make teachers' lives hell (which, given the retention problem in NYC isn't the best policy) but they're cost inefficient. When NYC teachers are asked to cover another class, they're paid at the per diem rate of around $40/hour. I don't know exactly what subs make, but I guarantee it's less than that.