@Deeppak Judging from this first post, you seem to be creating yourself and your child a recipe for disaster. Please correct me if I am wrong, but I see several issues:
- Your child is in 6th standard and it will probably be at least 6 or 7 years before he/she applies to the IIT's or MIT or other universities. Do you even know what your child wants to do in life? If your child doesn't want to study engineering, mathematics, biology, physics, or related fields, I am not sure why MIT is the best fit. If it is because of prestige, then that is not a very good reason.
- You referred to the GMAT and GRE in your post, which indicates you likely don't know much about how admissions works in the US. And you shouldn't need to know about them for several years. But those tests are not used for undergrad admissions; typically the SAT or ACT, SAT subject tests, AP exams, and TOEFL are more important.
- MIT is one of the most selective schools in the US and is even more selective internationally, to the point that it would be unwise to fix yourself on one school.
I agree with the above posters; let your child do things he/she likes, be a mentor, definitely encourage your child to pursue passions, and worry about college admissions in a few years.