A couple of things that are probably important here. In science, theory isn't just a guess. It has a specific meaning.
Evolution, in general, doesn't deal with the beginning of everything, but only with how things evolved once they were started. That beginning-of-everything is an important question. Absolutely. However it isn't a question related to the studies of evolution.
We are talking about what we teach our children. If we teach them that science is a matter of *poof* then chances are in 150 years we will all be speaking Chinese. Teaching that solving problems is a matter of prayer is probably not a useful use of school time. If we really believe we pray to end droughts, disease, and pestilence then we do a dreadful disservice to us, our children, and America's future.