It's simple. Children who are diligent, dirtied by their parents do better at school, but they are usually more stupid and think in a standard way, due to which they get better grades. Other normal children who are no longer assiduous are infringed upon by the teachers' grades. And in the university, the pressure of parents decreases and everything differentiates, as a rule.
A group of factors affects the success of training. These are personal characteristics, including interest, and the notorious intellect, and features of the nervous system. The first two points are described in detail above, I will pay attention to the last one.
The process of perception and processing of information is extremely complex. The brain structures that carry them out are extremely complex. And if it "gets lost" in some section, it affects the operation of the entire system. Some of these "failures" are not a medical pathology, but only form the style of our cognitive activity. If a person does not understand his peculiarities of information perception, then it will be more difficult for him than it could be.
I am inclined to believe that it is primarily about three things, none of which has anything to do with genetics and innate abilities.
Interest in learning / learning in general and in specific subjects in particular. A child who is interested, who wants to know and be able to do more, learns much more diligently and extensively than those who are pushed only by grades and abuse of parents. In general, in my opinion, one of the two main tasks of modern school teachers is to arouse students' interest in their subject (the second is to answer questions and help with the search and analysis of information). But this interest can come not only from teachers, but also from parents.
This is discipline, the skill to wade through routine things and finish the job. Even in the most interesting and exciting business, there are moments (and quite a few) through which you just need to wade through, just take it and do it. Boring, uninteresting, dreary, monotonous, but necessary. The child's skill of following this "must" must be developed, and must be developed even before school in the process of education.
Correct guidelines and desire for achievement. Socialization is a great thing, but only when you have the right skills. Very often, children begin to orient themselves far from the best representatives of their environment: they justify their behavior and their low academic performance by referring to others. It's easier than reaching out and trying to be better. But if a child is accustomed and brought up to reach for more, to want to be better and to be the best (without fanaticism, of course), this will not be a problem for him.
And so yes, some innate inclinations, of course, play a role.
It seems to me that motivation plays a major role here. The person sees whether education improves in any way the quality of his life. I do not believe that expensive gifts can radically change something if the child is not interested in learning. By my own example, I can explain that my parents never gave me monetary rewards for my studies, except for symbolic gifts, but this is not the point. But I clearly saw the reasons why I should pay attention to my studies - this is respect from teachers and classmates, much less hassle - no one dares to yell at me, no fear of parenting meetings and checking diaries. Although how to explain this if my classmates, who are in the same conditions, did not seem to put in a minimum of effort to study? This is such a simple motivation at the level of the society of the school itself. Some people by the end of high school become worried about their future fate, already decide what, in their opinion, will be useful in life, and pay more attention to these subjects. I know people who learn simply out of boredom. But this cannot be worked out in the sociable people who are rarely at home, except to take them to the village along with a bunch of textbooks. In general, it is very important to define the purpose of education. I often hear questions like, "Why do I need mathematics? And why physics?" So think about it. Maybe, really, there is no need for someone? (Although mathematics can be useful to many people in life, this was not the question). Mathematics is not needed, so at least USE scores are needed for admission. Some people are sure that their life will be fine even without education (a typical example, "parents will arrange, dad will take a job"). This is the problem of education. Probably, there is an inborn element too. It is not for nothing that this division into "mathematicians" and "humanities". Someone just doesn't understand these moths and arcsines, someone doesn't remember the date. But if a person wants, he will find a way. He will spend more time and energy, but he can. And he will be pleased with himself.