prejudiced, congrats on your son;s result. Unfortunately Sport's DS can only get a place at a selective school if they appeal, if they are successful he would be considered to be eligible for a selective school - it won;t happen automatically just because some others don't take up places.
It had happened automatically before. I know a girl in year 10 Townley who did not pass or deemed selective, I cannot remember the marks but she was offered a place in August. She had even bought blackfen girls uniform, looking forward to start in September before she was offered a place. This is without appeal.
1st put the name of the Grammar schools of your CAF form, then after that you can now appeal in March but make sure you get a very good support and reference from your headteacher especially on character, academic performance especially if he is very good in Maths and working at level 5. You have to convince the panel why you want him to go to that particular Grammar school.