You say this every time, and I repeat everytime, your son got lucky that you got him an ST in that season, had it been 2 seasons later, he'd be not priority 1.
Also, this scenario means that an adult will have to take you and gain you proirity, no chance of a young 15 year old lad to sign up one day with his mates, as he won't be anywhere near top priority.
The high priority gets further and further away every year for those with less than 500 points, I think about 3/4 games have made it to all STHs so far?