Firstly, he needs to explain to his parents that today's world is a vast ocean of opportunities. Everyone has his own individuality, which needs to be respected by the world. If someone is not god in maths or science, doesn't mean he cannot pursue anything in life. There are other great rare fields of cognition touched by people of the era, which can be pursued by one who is good in the respective field.
next, coming to the career options, he can either study literature, become a historian, or a geologist, as of a broad classification.