Apple Pencil - Cheaper Alternative?

First time I have ever heard of an Apple pencil.

I’ve seen some on eBay and amazon that look very similar but not sure what the quality is like as never purchased one. Depending on how much you want to spend it might be worth getting a second hand Apple Pencil as the price difference between a fake one and a second hand real one sometimes isn’t that much and it’s then worth getting the genuine one. Hope this helps.

Is apple pencil just a stylus or does it do something that a stylus doesn't

The school are recommending an Apple Pencil? That's a bit irresponsible. I think you'll be fine with any standard stylus. What will he be doing with it? I'd figure that out first and then look at the specs and reviews.

Also, the Apple Pencil is a product designed specifically to work with certain iPads. It's as useful as prodding your iPad with a stick if not. The supported models are on here: https://www.imore.com/which-ipad-models-support-apple-pencil. I'm doubting a school would expect parents to own a recent iPad and £130 stylus to go with it.