How old is your DS2?

I think sometimes as parents we can be emotional about issues concerning our kids. We have every right to. It is our maternal instinct to protect. Not saying that you are being unreasonable, just sometimes we don't see the whole picture.

Am I right in thinking that he had numerous spelling activities he could choose from to complete his spelling and he didn't choose any of them? Hence him having to complete two spelling activities at home? I do think there are some tasks children need to complete and should not always be able to move on and be 'rewarded' by getting out of it IYKWIM. Have you spoken to him about it and why he didn't complete it?

I would maybe organise a meeting with the teacher. Try and get to the bottom of why he is choosing not to complete his activities at school. What techniques she uses to try and get him to complete tasks. You may find she has gone through a range of strategies with him and he still didn't complete it in that time so she has sent it home to do. If she hasn't gone through a range of strategies and just let him sit there, then that is very poor on her part.

I also highly doubt the teacher didn't prompt the class to hand in their homework. I know I can stand up the front and say 3 times has everyone bought their homework in and notes, lunch orders, etc. and there will be kids that hand it in at the end of the day because they forgot they had it in their bag even though I have asked 3-5 times! This does teachers heads in! There is only so many times you can ask.

Again I don't know this teacher, I am just trying to see it from the other side as well.
Hopefully you can get to the bottom of it so that your little man is happy at school once again.