Hello riyazulhoque,

As you want your child to get into field of medicine through neet, there are some books like science Olympiad or science companion which can give your child a basic knowledge about science and when your son will be in 6th standard he will get to study the biology,physics and chemistry as a separate subjects where books like NEET FOUNDATION EXPLORER or 6th SCIENCE FOUNDATION etc will be helpful ,later on every year will have foundation course books for NEET preparation till 12th ,so  first know that does your son's schools provide such foundation course for NEET if not then you can get these books online, with help of biology, physics and chemistry puzzles and games you can make NEET preparation more interesting for your son from childhood itself ,in this way you can mould your child in the appropriate way,

All this could be possible only of your son is interested in the science ,

All the best !!