I think many posters here are out of touch with inner-city kids. It's a whole different ball game than suburbia.
I can well-imagine why the girl didn't tell her mom. Her mom probably was a working single parent who was not home.
I can also understand the culture of "snitching." There were fights, gang problems in the school where I taught. NO ONE would say a thing. Snitching is not socially tolerated, and there's no way anyone is going to change the culture of snitching. It's not necessarily being afraid; it's just not something that's done.
Again, an inner-city bus with 60 kids? If you've never been in this situation, first of all, don't even think quiet. Think so loud that you cannot hear what the person sitting next to you is saying. It doesn't at all suprise me that the driver didn't know the penetration was happening. There were no aides on the bus. Buses today need aides.