At 4th grade I totally and definitely wanted to be a military jet fighter, and stayed in that phase for a solid 3 or 4 years. I'm pretty glad I learned other things as well.

Sure, making a decision is possible, and parents have the authority to deal with the aftermath. The same way some decide their kid will be an elite pianist and commit 100% to it as soon as they can.

But I don't see it as a sane path in general.