A school/library should not waste money on a $4000 computer.
It's not a waste of money when you bring expensive equipment to tens of thousands of people to use.
A single $4k computer for a 1000+ student school should be an afterthought, spread that cost over 5 years and the cost per student is minuscule. This is not a Chromebook you get for every student, you'll need one or two max - unless the school specifically focuses on A/V production.
This is equally true for a $10k computer, spread over all the students. It's great to save money. But Apple's diversity claim just doesn't add up.