"Train up a child" isn't talking about disciplining your toddler. Now Proverbs 22:15 does talk about that 9 verses later, but it uses a completely different term for "discipline" and for "child." If you go to an online Bible concordance like www.studylight.org (my favorite), you can use the interlinear Bible to find out the Hebrew word translated "train." When you look up that word, you'll find that it's used only 4 other times in the Bible as a verb and 8 times in noun form. Every use of that word refers to initiating or dedicating something for a unique purpose (such as dedicating the Temple). Corresponding words in Egyptian, Akkadian and Aramaic confirm this ancient near eastern meaning. So what?
The evidence demonstrates that common interpretations have got it all wrong. Proverbs 22:6 does not command people to discipline or teach their children a certain way. There should be no debate about whether the passage instructs parents to either teach children the way of wisdom, righteousness and life or teach them according to their personalities, capacities and temperament. Both interpretations are wrong.
Initiation Rites for Future Leadership Roles
Proverbs 22:6 actually commanded wealthy parents of great status to initiate their adolescents into societally significant roles they were to play. The word translated "child" in most Bibles actually refers to adolescent or teenage squires who would take on prominent roles in the royal court. Hebrew does have words for "children" in general (e.g., yeled), but Proverbs is specifically addressing sons with significant status using the term na'ar (see Hildebrandt, "Proverbs 22:6a: Train up a child?," Grace Theological Journal, 10-14). Proverbs 22:6 wants to make sure that such children of privilege were ushered into their responsibilities properly. Such instructions targeting wealthy children are not unusual in Proverbs. Most proverbs were wise sayings taught to wealthy adolescent males in the royal court. In fact, the immediate context of Proverbs 22:1-9 contains many Proverbs targeting that wealthy audience.
Once you know these facts, Proverbs 22:6 is better translated: "Initiate a wealthy young man into his proper role and when he is old, he will not depart from it." It's not talking about disciplining a 3-year old. So I go elsewhere for advice on that (see Proverbs 22:15 and 29:15 where parents are told to discipline and prevent their privileged children from getting their own way). Proverbs 22:6 is, however, telling me how important it is to initiate my children into distinguished roles that they will play in life.
When my kids are ready for higher levels of responsibility (in the adolescent years and beyond I suppose), I will look for opportunities to mimic the ancient royal courts and the privileged parents who initiated young squires. The proverbial principle is translatable even though the original context of courts and squires has disappeared long ago. I guess that could mean honoring my kids when they get their first leadership position or first degree or when they master a skill that can greatly benefit others. These significant rites of passage deserve personalized graduation ceremonies of sorts. No matter what specific rites of passage you might choose, the goal is to recognize and dignify every esteemed role that children take on in hopes that they will continue down that path the rest of their lives.