My child is best- He is topper 

You should make your child feel that he is best but never put extra pressure on him to do better than what he can really do, that is like mental torture for him. Most parents try to put extra pressure on their children to do ‘best’ and nothing lesser without evaluating his capacities as every one has a limit and pushing him beyond that would only make things worse. The fact is that every parent is looking for 98-100% range of marks, which is not possible for most of the children and there begins the problem.

I want you to be at first position in class

That is not fair! This only makes a child do worse than what he is capable of. He becomes disturbed and keeps thinking all the time about possibilities if he would not come good to the expectations of his parents. Moreover, that can bring overall bad results, in exams and in life if the results are not as per expectations therefore this is not advisable to put unnecessary pressure on your child. Your job is to see to let him do his studies according to his mental standard and capacity. You should only see to it that he is doing his job in a proper way with out going in wrong directions. That would make him free from undesired pressure and he would certainly do far better although that may not be as per your expectation but not every one is destined to be an Einstein any way. How can every one be at first position in class unless there is just one student in a class?

Your job is to see to it that your child does best as per his capacity and not best among the class or group. You should see to it that he is doing according to plan and timetable chalked out for him. You must tell him importance of education but never pressurize him to do beyond his capacity. You shall have to change your outlook and see the ground realities. Once you know the actual mental level and his capacities, you shall not feel disappointed. 

Lack of practice and sense of nervousness 

Some children have problem of sense of nervousness, which makes them forget their lessons despite their best efforts. They do their best to remember what they study, even they recite it in presence of their parents but when the time comes to write it on answer sheets they tend to forget whatever they learnt and every thing goes out clean from their minds. There is a reason behind this ‘clean slate’ behavior in some children. The tendency to do every thing at super fast speed only helps them to remember the lesson for few hours, as they do not practice it properly. At this stage, children need to revise their lessons by writing it repeatedly unless they are blessed with extra ordinary memory power but not every child is capable of such powers. The result - they forget their lessons after some time to feel disappointed when they cannot recall it in examination hall.

I can remember the time when parents used to make it a point to ask their children to write every thing using their memory so that every concept became clear and even their writing skills improved also they were able to write it within stipulated time. The teachers should also keep this in mind that they should complete their syllabus timely to give children ample time to revise their course to do better in exams.

If your child is not doing as per your expectation

He will not do it according to your wishes just because you want him to do it that way. If you think that, your rude behavior can improve his skills that are your misconception about the whole matter because no matter how harshly you treat your child he would not do better but may become more dull, afraid and uninterested. Your highhandedness would not make him any wiser than what his mental standard permits him. 

You can make him sit for study but you shall see to it that he does it properly because mere reading would not make him understand the subject properly. You should know the psychology of your child. You can make him sit but not study for him. He cannot do all the study in a day to obtain 90+percentage to satisfy your ego, he has own limitations. You must behave friendly with your child to boost up his moral and make him confident to share his problem with your freely. That will certainly bring the matter under control while you shall know him better and help him solve his study problems; there is no other way out. If you keep the following points in your mind, maybe you can control the problem up to some extent- 

Conclusion

Parents who think that their children should be among the toppers without knowing their mental capacity are only making things worse for their children because such children find themselves under extra pressure. They try to come good to the expectations of their parents but while not finding them anywhere near there become frustrated and loose interest and some times do even worse than they are capable of doing. 

Therefore this is suggested to not to pressurize your children unless you understand them and their problem fully well because pressure may make your child unsettled and he would not know his problem properly. He would feel depressed and inferiority complex would take over him. He may even suffer from exam phobia to make things go totally out of hands. 

Note- Photos from wikipedia