Make a virtual account on selfwealth. Load it up with $50k of play money and see how it goes after a year. My high school had a thing called sharemarket game which was along these lines. With a virtual/pretend account they can try their hand at it for a while and see how they do.

Barefoot Investor

I remember this from high school.

https://www.asx.com.au/investors/investment-tools-and-resources/sharemarket-game#:~:text=Students%20receive%20%2450%2C000%20in%20virtual,to%20several%20subjects%20Australia%2Dwide.

I didn't read too closely, registrations might've closed already but might be worth sending to his school for next year.

I used this site to learn the basics and help me to make an informed decision: Motley Fool Australia

I can't give you any info about which apps/sites are best but I know there are practice investing sites out there where you invest in the real market with fake money to see how you go. This was many years back when I last looked at it but it was free to give it a go. Then you'd want a site/app where you can invest small amounts with low brokerage fees, which I don't know if you can get around paying. They might actually have articles on that stuff on Motley Fool, not sure.

Check out ‘The Ulysses Contract’ by Michael Kemp - has info on share investing. There are platforms he can use to diy trades without a broker (e.g. cmc markets). I also love the idea of virtual investing as a trial run, as others have suggested - that would be a great way to learn without losing $.