It is the best if parent can bring the kid to school/school bus by himself/herself.
I frequently remind my helper that she must follow traffic lights and she will be subject to a penalty of $1500 (?) if she breaks the rule. She is afraid of being charged and giving her money away. I clearly tell her that it is a must to pay full attention to my kid on the street. I will go out with her many times to ensure that she follows traffic light and holds my kid's hand on the street.
Whenever there is accident concerning domestic helpers, I will tell her or show her the news on newspaper/TV. It is an act of "friendly reminder".
True, its the best to do it by ourselves. But somehow not every family can do the same and we just can't tell it's rite or wrong without knowing the situation in individual family.