I am a bit confused, what is the difference between a grammar and a super selective?
This is my understanding, but I'm willing to be corrected!
A local grammar school has a catchment area, so is nominally for dc in the locality, and sets a pass mark for its 11+ exam. If a child achieves the pass mark, whether only just, or near the top, then a place will automatically be offered unless the school is over-subscribed. In that case places will be offered using a number of criteria, giving preference to children who, for example, are 'looked after', in receipt of pupil premium or live closest to the school.
A super-selective school doesn't have a catchment, as such, so is open to applications from a wider area, and doesn't have a pass mark, but simply offers its places to the children who have achieved the highest scores in the exam, until all the available places have been allocated.