I am a land and seascape photographer.
I am not a portrait photographer.
First off I am going to mention the things that i would "fix".
The little girl front middle. I think her face is too bright and the photo would be better if you could darken her a bit to have the tones more closely aligned with the other children.
And composition, faces are basically lined up along the middle of the photo. It looks much better if you crop about a foot off the top of the image to let the kids "stand taller" and fill the frame.
Now, some more general and specific comments.
B&W - I know you did it to cover a deficiency in the image, but I think its a great choice anyway. I think it is wonderful as a mono image.
Composition, the chair edges are cut off, I don't think it matters a cracker.
Yes it would be more "perfect" if all of the chair arms were included but then the children would be slightly smaller in the image.
And to be honest, it is these slight "imperfections" that i love about this image. They give it a ... humanity ... a candidness .. a mood, ...that adds so much more than perfection would.
The childrens eyes, looking different directions and mostly not looking at the camera. Usually a big no-no with group portraits. Another "imperfection" that works perfectly.
Perfect in its rule breaking, very well done.
The facial expressions, I love that they are not all just smiling looking at the camera.
It gives it life, vitality, individualism, truth.
This is very very good.
For me - it is perfect in it's "imperfections".