The use of even if would also be correct in this case.I am going to school, although it is raining. --> Correct, two facts are being expressed going to school and it is raining.I go to school even when it is raining. --> Better, the sentence means that I will go to school whether it rains or not is it raining right not? may be or may not be (hypothetical).I go to school even when it rains.