Unfairness

Mum just called. She say I got 36/42. While Sandra passed the subject mum say 1st time she pass all subject then mum even say gona reward her then i say eh, i also pass all my subjects leh i should deserve a reward too. but why mum say no? i even pass all my subjects for all the lvls so far... I don't know what i should do so unfair i pass P1 also i dont get a reward P2, P3 till P4 i passed all subjects but dont get anything in return.