Yes, it is. First off, you're not just dealing with the students, you're dealing with (sometimes) batshit-crazy parents, in addition to your own supervisory chain. You're dealing with 25 students in a room, 12 of which have IEPs or 504 documentation, and you may or may not have any in-room support for those kids, depending on the subject area and district. And you're having to deal with students who just won't do the work or are disruptive, you're likely to get little support from the school in terms of disciplining the kid, and often less from the kid's parents.
Most programmers - most professionals - don't have to deal with that many individual people - and aren't expected to both cater to them and produce results - to the same degree as teachers. It's exhausting. And when you look at what charter schools are attempting to get teachers to do (and mind you, the charters often do a crap job of actually supporting their teachers), it's little wonder that a high proportion of charter school teachers quit after one or two years. BTW, the least effective teaching years for a teacher? The first two or three years. If your school has a high percentage of teachers with less than four years of experience, it's not going to be as good. I'm sure some of the /. readers will object to that, but there are a significant number of studies that have shown it over the years.
In addition, there's the pressure that if you can't get through to a kid, they're behind next year, and maybe more the year after that. And trust me, that bothers them. You're constantly battling to get kids to recognize that something is in their long-term benefit. Most goddamn adults can't figure that out.