dealing with horrible kids through my job

Although working for the Public Schools has awesome benefits and retirement, i feel like i can't work with kids as much as i thought i could. I'm an Assistant at an elementary school and I'm very well liked by the kids. I've never been mean but I've been strict. Well today i was helping out in a 3rd grade class (8 year olds mostly) and I'm obviously pregnant. Well i was talking with a couple of the children about my baby and this little girl comes up to me and says "I really hope your baby dies." i was speechless! the kids at my school are tough as it is but hearing that broke me! i reported it to my principle and he didn't seem as concerned as i had hoped... he said "It's not okay that she said that BUT it is also okay because you need to understand where she's coming from." As in maybe there is a personal underlying reason why she said those things.. and that she is "just a kid". That was NOT what i wanted to hear. On top of that, when i miscarried a couple months back i had 2nd graders telling me they were glad my first baby died.. i don't know what to do but i feel like i can't work with little brats like that, ESPECIALLY when pregnant! I'm due in the middle of the year so it's not like i can up and leave because I'll be out paid maternity leave.. and if i go to a new company I'll probably lose my insurance and won't get maternity leave because I'd only be with the new company for several months. I'm so furious and confused and stressed out!!