What's bad about passing a school bus? Were they passing it on the right-hand side?
The article forgot to mention that but the assumption is that (a) a reasonable driver would know that and (b) their audience probably remembered that happening, since it was only a few months ago IIRC.
We don't really have school buses here in Spain so I've never seen this phenomenon.
Many school buses have stop signs that extend when they have the doors open to help remind people of this and prevent the little overzealous street crossers from getting splattered.