In season progression is different for CPU and Human controlled teams. Human players will progress more as they will have a much greater increase in AWR over the course of a season. CPU Post Season and Hum Post Season progression is all done on bell curves.
The game uses an empirical rule bell curve to determine how much each team should progress in the off season. The mean of the curve is adjusted by the prestige of the team. So the mean of the curve would be higher for high prestige team and lower for a lower prestige team, but a lower prestige team (say 3*) could fall 2 standard deviations to the top end of the curve one year while a 5* team could fall close to 2 standard deviations to the bottom of their curve and the 3* team might progress a little better than the 5* for that year. Most of the time though (68%) the teams will fall with in one standard deviation of the mean.
This is just an image with 3 bell curves on it. The numbers are not important to the concept of how the game progression works. Think of the mean of the first curve as being for a 3* team, the second curve being 4* and the last being 5*. You will see an over lap area when the highest of a previous curve might be higher than the low side of next curve. In the game the means of the curves are more spaced with a little less overlap of each bell curve than what is shown in this graphic.
Also you might want to check out my thread on NCAA 2013 on how player ratings effect the overall of a player.
Here. Based on where each team falls on the curve the players ( based on what his position is) will get boosts to certain skills that will raise his overall. How much of a boost to each still is based on where the team falls on the curve and which curve they are on.
I hope this has been clear enough to help give you a better understanding of how the progression works.