Why break a system that demonstrably works?
My question is for the students, does it matter if it's a YSB or coach or a service bus? The answer is fundamentally No.
Removing the YSB requirement and allowing closed school routes to be ran by normal coaches and buses means huge changes for operators. It opens up more money making opportunities which generally means there are savings for the schools since operator costs are spread out over more work. Some operators will choose to run local service between the schools as well. In the UK, an operator told me just a few years back 'I make a salary off schools. I only run the service stuff for pocket money', if that logic transferred over to the US, there could be a bigger commercial bus network.
If you go down the tendered bus route, as we have seen here in the UK, it's much cheaper for Local authorities to contract out 'between school' runs than it is for an all day bus.
The yellow school minibuses could be used on ring and ride between schools (as happens here in the UK). Again, cost savings for authorities and opens up opportunities for operators.
I'm not talking in riddles here, I can't see how what I am saying is being misunderstood. By making the law change with YSBs, you make cost savings and that means with the available budget, it allows bigger and better bus networks for much lower cost than at current.
Bigger bus networks encourage people to use the services
More people using the services is less people in cars.