Just curious, it seems some schools have sibling / alumni policies? If a child passes the first stage (the academic stage) are they guaranteed a place? Kings College Junior school:
Where a candidate has a sibling with a current or very recent connection with the junior or senior school, the school reserves the right to take this into account so that a pupil of sufficient ability can attend the same school as his sibling.
SPJS:
St Paul’s School welcomes applications from the brothers of current and previous pupils as well as the sons and other relatives of Old Paulines. Candidates will be assessed alongside all other candidates and be expected to comply with all aspects of the admissions process including deadlines and meeting the stringent academic criteria for entry.