"Do you believe in God, sir?" I imagine that this is a question that science teachers, like me, get asked far more often than, say, English or Geography teachers. I usually answer with a simple "no, I don't", but I recently answered this question by saying "what do you think?" to which the student replied he thought I was probably an atheist because I was a "scientist". He was right about me being an atheist, but I was an atheist long before I was any kind of "scientist".

My student needn't have been right – not all scientists or science teachers are atheists. I've worked alongside religious science teachers and some of the greatest contributions to the science have been made by people who believed in a god. There are some people who would say that there is no conflict between science and religion but young people brought up in religious homes are not necessarily taught this and a few will even have been taught to believe the opposite. I know that some of my own students are struggling to reconcile what they see as contradictory approaches to understanding the world. I suspect it's particularly difficult for those who enjoy science, and are good at it, but come from particularly religious families.

I'm a physics teacher and you might think that I get away without too much of this sort of conflict in my lessons. You might think it's mostly the biology teachers, the ones who have to teach the theory of evolution, who have to deal with the awkward situation of teaching something that flatly contradicts the religious beliefs of some of their students. But it's not. And it shouldn't be. The truth is that all science teachers must deal with the fact that, if they are teaching science properly, their lessons will necessarily challenge the religious beliefs of some of their students.

Despite appearances to the contrary, science in schools is not just about teaching facts and figures, it is about teaching the way in which humans have arrived at answers to questions ranging from how life reproduces itself to how the stars shine. Science lessons should equip students with critical thinking skills, the most important of which is to ask for evidence for claims about "truth". If we've succeeded in teaching these skills, it's inevitable that some of our religious students will ask "what is the proof for the existence of a god?" and it's inevitable that some of these students will not be happy with the stock religious answers to this question.

I have been surprised at the number of students I meet who have been brought up to believe that the holy book of their particular religion contains the literal truth about the origins of life and the universe. As a physics teacher, it's my job to make sure that students appreciate that we have good reasons to believe that the universe is about 13.7bn years old and that it is filled with thousands of billions of stars. It is my job to teach that the earth was formed about 4.5bn years ago from the remnants of an exploded star and that we too are made up of atoms that came from that dead star. It is my job to teach that scientists think that everything, literally everything, came from a tiny point that exploded, creating time and space as it did so. More importantly I have to explain to them why we think this, and to admit to them that we don't yet fully understand how or why this happened. I try to make clear that science is not certain about these things, that it's about constantly trying to improve our understanding of the world and being open to the idea that we may be wrong.

If my colleagues and I do our jobs properly, our students should go away with a story about the history of life and the universe that is far richer, far grander and far more detailed than that presented in any religious text. More importantly, they should go away with an understanding of how and why this story has been written. If we do a really well, some of our students might even go away knowing that they can become co-authors of this story by becoming scientists themselves.

I'm not suggesting that science teachers should seek to convert children away from the religions they have been brought up with, or tell them that God doesn't exist. However, I can't help but feel that a proper science education should equip young people to arrive at their own decisions about what to believe, and ensure that if they do conclude there is a god, it is a god who doesn't stop them from fully appreciating the truth and beauty of scientific knowledge.