Long Term putting Spider-Man in high school will be the best decision they could have made. Sony and Marvel have an actor they can use for 10+ years that can also become the new face of the MCU once RDJ's Iron Man is retired.
Now that I'm thinking about it the decision to have an older Batman while short term may make for a more interesting take on the Batman story it also means fairly soon (ignoring all rumors of Affleck's imminent departure) WB is going to think about a succession plan. And will the general public be interested in an non-Bruce Wayne Batman?
Interesting times ahead.