For what it's worth, a recent EDB survey shown that 'HK Local' and 'Chinese' represents the top two student nationalities in YC Primary (around 41% and 27% respectively).
'HK Local' refers to HK permanent residents without foreign passport (except BNO).
'Chinese' include those who hold Chinese nationality and are not HK PR, such as Mainlanders, Macaoese and Taiwanese.