Just going to echo what a lot of others have said -- don't answer during school time and realize that your life is crazy-hectic right now and you have to take care of YOU and your KIDS.
I don't know your whole situation, but someone else mentioned that you might have a hard time saying "no" to family. I used to be that way - I would never ever choose to not take a call from them, because I would feel guilty about that. I felt like I had to always be emotionally available to them, and to do otherwise was mean. Not so!! Through a long and painful situation with them (story for another day), I realized that I CAN be my own person and still give them a healthy amount of love and attention.
There are times that my brother calls (he calls everyone when he is driving to and from work) or my sister-in-law calls, and I will be busy with the kids or doing school, etc. and I don't answer. And you know what? It's OK. People understand that having kids is huge and that we don't always have time to sit and chat.
I do try to find time somewhere in the day(s) after the missed call to call and chat, but that doesn't always happen.
Hang in there- and I have to say I'm glad I'm not the only one who can't juggle the phone calls and kids at the same time! It's like, when I am on the phone DD starts doing every single thing she knows she is not supposed to! I just got tired of trying to juggle and shush her (like you said, not fair to her!) and it would exhaust me and make me feel pulled in a zillion directions.
Anyway - long post to basically say what others did.

Hang in there!! Enjoy your down time.
