This might not be needed today, but will surely be needed in years to come. Getting this done now at no additional cost to the school is fantastic. I'm on the Board of Trustees for our local school and there is no money to allow for this kind of expense when it is necessary. There are more and more devices in the classroom and this is only going to increase in months and years to come with bring your own device.
Kids are making video presentations, streaming content and doing most things online nowadays.
Doing nothing would be a mistake (in my opinion).
Purely looking at it from a future proofing funding situation sure.
As @bartender pointed out, this would make routing LAN content difficult, you would need to be routing on each classroom, aggregating at BNG or such.
also need to remember the fibre is the cheap part.
the hardware to realistically make use of 1gbit within a classroom will easily set you back far more.