At our school..
Maths - quite excellent. Some teachers are better than others, definitely, but as a whole they are quite good.
English - this department is quite a mess. DISTINCT differences between teachers, there are definitely some good ones, but definitely some not so good ones as well.
Science - mostly dud. They teach us nothing, expect us to know everything. My physics teacher is so lazy nowadays that she just prints hsc online for us to read in class -_- and as such, phys is the only subject I have a tutor for. The head teacher is the laziest person in the whole department, but he's probably also the most knowledgeable.
Social Sciences - ranges from "no idea what they're talking about" to "absolute genius but cbf". I think my teacher is "no idea what they're talking about" haha. Sincerely wish I had another teacher for this subject, but tbh with eco it's not so much of a loss, I basically self-learn the syllabus.
PD - from what I've heard, they teach well, but mark far too easy. Not the worst but not the best dept.
IA - my sources tell me - quite dud. I think they KNOW things, maybe, but most of them never seem to have any idea of what they're doing.
Languages - Great. We only have jap and latin classes in our grade and they both think their teachers are great.
Histories - probably the department which has fallen from grace. It used to be excellent in the time of the legendary Bruce Dennett (look him up, he wrote a history textbook), but now we've been getting worse. The last year Dennett taught was in 2008 - take a look at the modern state ranker list for that year and you'll see what I mean.
Music - no idea, I don't know the new teachers. This is like the defence against the dark arts department, I think in the time I've been at this school we've had 5 or 6 new teachers of music come and go.
D&T - really only there for the sake of the junior school
VA - quite good. Normally there's one class, and the head takes it, and he's quite a good teacher.
As you can see, GENERALLY the teachers we get are quite good. Sometimes I DO wonder how some teachers can even be qualified to teach at our school.. @___@