I understand where the OP is coming from. I have one who has talked of going no where else but a specific university for many many years. As parents, we know what will be required to actually go there. If he mentions taking it easy in terms of courses selcted in high school, then absolutely yes, we remind him that is not the course to get him where he wants to be.
We expect all of our children to do their very best. Whether it is 100 on spellings tests for one or a B in some other class for another, we expect them to do as well as we( and they) know is possible.
Yes, there will always be a college that will take most anyone, even with less than stellar high school records. There are also colleges that wouldn't look at a student with less than 1450 on their SATs. That's just the way things are. Course selection is VERY important, perhaps more than the grade attained in the class. Admissions officers do take into account the level of the course. If Honors sections are offered in certain subjects and the student takes the regular level, even with an A in the course, it is noted they were not in the toughest option.
This is high school though. Ten is different, but it isn't too early to understand one another's expectations. A 10 year old who dreams of becoming a physician is certainly capable of hearing what that requires. A child with academic promise needs coaching, just as an athlete does. If Michael Jordan hadn't held a basketball or a baseball bat until his senior year in high school, perhaps he wouldn't have developed the fundamental skills for his future success. Just as ballet is a progression, from learning the positions, to pointe shoes, to more demanding practice times, education is a path. You really can't jump on at the end of the path and expect to keep up with those that have been on from the beginning.
Yes, let a 10 year old be a little kid; play video games, catch crayfish, and run around the house, but also let them know that school and education are important and once a child expresses an interest in something, I think it is a parent's job to nuture and encourage it. With one who wants to go to one of the top schools in the country, we drive hours on weekends for enrichment courses. For one that wants to be a fisherman, I learned to gut a fish and found the best spot to catch the really big ones, and for one that dreams of becomming a ballerina, I spend countless miles and hours in my car driving to lessons. It is all part of encoraging their gifts and helping define the paths they have chosen for themselves.