AB
Train up a child in the way he should go [and in keeping with his individual gift or bent], and when he is old he will not depart from it.

CEV   
Teach your children right from wrong, and when they are grown they will still do right.  

DT      
Train up the child according to the tenor of his way, and when he is old he will not depart from it.

ESV    
Train up a child in the way he should go; even when he is old he will not depart from it.

HCSB 
Teach a youth about the way he should go; even when he is old he will not depart from it.

KJV
Train up a child in the way he should go, and when he is old he will not depart from it.

LXX   
Missing entirely!

NIV    
Train [or start] a child in the way he should go, and when he is old he will not turn from it.

NJB
Give a lad a training suitable to his character and, even when old, he will not go back on it.

NLT
Teach your children to choose the right path, and when they are older, they will remain upon it.

NRS
Train children in the right way, and when old, they will not stray.

TM
Point your kids in the right direction—when they're old they won't be lost.

VUL
Proverbium est adulescens iuxta viam suam etiam cum senuerit non recedet ab ea.

YLT
Give instruction to a youth about his way, even when he is old he turneth not from it.


Conclusions
* The Hebrew is ambiguous. "According to his way" is susceptible of several translations. "His way" =  in the way he should go (traditional view); in "His" (God's) way; according to his own personality (suggested in the 9th century by a Jewish commentator).
* The strictest possible understanding of the verse will be attractive to those who believe they can control the behavior of others.
* The traditional, stricter understanding of the verse may put too much responsibility on the parents, and too little on the child.
* Even if the KJV and versions influenced by it are correct, still we ought to keep in mind that Proverbs brings us general truths, not necessarily absolute promises (e.g. 16:3).