Accumalative advantage

What is an accumalative advantage? I believe that it is an advantage that adds up, or accumalates over time. Like a snowball rolling down a hill, the snowball will build up as it gets farther down the hill. This represents the supposed advantage  you get will build up over time. A major question that comes to my mind right now, is that does delaying when you start kindergarten, really gives you an accumalative advantage. I believe that it doesn't. I believe that if you start kindergarten late and with people who are not of your age group and less mature you're only holding yourself back. If you're competing with students who are a year younger, you're not really challenging yourself because you've had that extra year to mature, learn, and grow. On the other hand if your in a grade with people who are of your age group, you're challenging yourself more because they're on the same academic level you are on. What determines how smart you are in the later years is how hard you work and study. So all in all I agree with Wang and Aamodt.