I did the speed awareness course last year. We were told that the course effectively wipes your slate clean, but if you get stopped again within a certain period of time then you don't get the option a second time. And a third time? Well ... bye-bye driving licence.
Also, depending on the severity of the offence, the court could decide on a harsher penalty than a fine, even if it's technically just a 'three-point' crime. A lad on the course I did had been done for driving without due care and attention, speeding and running a red light all at the same time. He got an 18-month ban as well as being ordered to attend the course. He was 19 and brave enough to admit all this to the group, as well as the fact that if it happened again then he was looking at prison. He *said* he'd learnt his lesson but I guess only time will tell.
As the other two have said, your son does need to slow down though. At best he'll look a pratt and lose his licence. At worst he'll kill himself or someone else. I read far too many stories of someone's mate or girlfriend being killed as passengers because their partner was speeding, and I can't imagine living your whole life knowing you were directly responsible for someone's death.