All the right stuff is focused. I like the B&W monotone treatment. It's a real nice shot to me anyway.
I used the lightness channel in labcolour, CS5. At the moment I prefer that to the B&W in RGB. ( I suspect that I might have an issue with the screen on my laptop. That might be the reason I lift the shadows so much.)
Well, whatever you're doing it works. I like the shot of the class mates better than the flower. You really nailed the eye on that foreground girl/woman/child whatever is appropriate, and the lettering and pen on the whiteboard. Plus it is just a feel good shot. More than a thousand words kind of thing.
I agree abaout the flower. Low light and a big aperture on a small flower is not a great combination. Flowers in black and white isn´t much fun either.