can catch lots of tadpoles, but can't seem to catch a break

i was so excited yesterday. as todd finished draining the koi pond in our backyard, i thought i saw something moving on the bottom in the few inches of leftover water. once i got closer to the edge, i realized there were tons of little tadpoles coming to the surface and then burying themselves back in to the muck. so unlike me to get messy and yucky, i grabbed a cup and our old hermit crab tank and climbed down into the mess of our old pond. i sat in the heat for over 15 minutes, scooping our nasty fishy muck and felt such a sense of success each time i caught one and put it into the tank. when i felt like i had gotten enough and saved as many as i could from sure death as the pond water seeped into the dirt below, i climbed out and admired my new little project. i knew the kids were going to be SO thrilled. i set it out on the table and ran in to show the kids. they were, as i expected, so impressed and excited! then this morning, we went and checked on them and to our surprise some has grown so much and turned into froglets...frogs were coming soon. so we found a perfect rock to put in for the frogs to sit on and left them to enjoy their afternoon. well, we dug out all our frog books and i had a life cycle poster tucked away in the attic from when i used to teach, so we got that out as well, and have been researching all day. owen decided he would bring half of them to school to let his friends experience the excitement too. well, i went out just a bit ago and i saw no movement. i ran over and all of them were dead! all of them. i feel like such a failure! i cannot even get the natural process of life that was working just fine, to proceed. the kids are going to be crushed!