Stressed, is there any way you could all get some time out? Could the puppy go back to the breeder for a couple of weeks, or to a dog trainer?
I was really not enjoying our devil pup either. We had a really good behaviourist in, but it was so much effort all the time. I couldn't even cuddle her without her biting me.
We've just been on hols for 2wks. Devil pup went back to the breeders, so she was with her mum, a brother and 2other dogs, plus they day sit another of her siblings, so she had full on dog days as it were. Think a combination of them being really experienced and calm with her, lovely rowdy bitey puppy play, and our initial legwork paid off. As she was biting and being bitten by her siblings, I think she learned bite inhibition, and also now 2wks older so she's calmer coming back into our home.
She's not perfect by any means, and we've had a bit of devilling today, but mainly jumping and stealing toys to chew, but importantly no biting of humans. This is just such a bonus to me as it means she can be with us all more without me constantly panicking that she'll bite the DC. She's happier too, which I think helps. Dogs are sociable animals and need contact, so by being with us more, she's calmer too. Think when she was separated to much, it was too exciting when she did come into contact with everyone IYSWIM? Now, I think we've become a little boring as we're there all the time, so she's not so hyper with us, and is just lying down next to the DC as they play, rather than trying to maul them.
I really think you need some time out away from the pup. It did wonders for us. I don't think you need worry about school volunteering-just pop the pup into her crate for a couple of hours...
Hope you can work things out. I know it's difficult, but when you're this upset, dogs pick up on it, and get confused and more upsetting. If you have time out, then maybe things will work out for you as it seems to finally be doing for us,x