First of all you need to decide whether atheism is a religion or not. To do that you need to decide on your definition of religion.
Some might say a religion is a system of faith and worship. This would not apply to atheism as, by definition, it denies the existence of a being worthy of worship. Atheists would also say that they accept the scientific method alone, in deciding whether something is true or not. Others may not see atheism in this way. This is something which we study at A Level if you choose to take it.
Atheism seems to be growing in European countries, but this is not so in the U.S.A. or some countries in Africa. During the last 150 years or so, the discovery of scientific explanations for matters which were previously attributed to God, seems to be the main reason why people have abandoned traditional religious beliefs. For them God is no longer required as an explanation. If you choose to take G.C.S.E. R.S., this is one of the topics we study.