While I want to sympathize with you, I am reminded of

the question in that familiar story: "Where is the control?" In other words, how do we know for sure you'd have been happier if you had not skipped the two grades? Where is the control that rules out the possibility that you'd have been equally miserable (for other reasons) even if your dad had not made the "absolute right" decision? After all, to let you stay put with peers of your own age would have been as much of your dad's decision as a decision to the contrary. How could he have predicted which decision would result in a happy and healthy daughter? Suppose he had let you stay put and you had felt miserable later on and blamed such misery on his decision?

You are right to say he should not have declared his decision infallible. The truth is nobody really knows in many cases. But then again, how can anyone be sure you are right in attributing your misery to his decision?