Great question! There are some interesting questions you can ask, but the best way is to show it. Even better would be to experience it. For 8th graders, this can perhaps be a nice suggestion:

Ask them where the money on your bank account is stored (centralized, 1 point of failure). Then show a Bitcoin wallet with some sats, preferably on a screen/monitor... E.g. Sparrow wallet or Coinos wallet with a self-custody wallet (coinos.io) wallet for a simpler UI Ask them where those Bitcoin are stored.They probably think it's inside the wallet, while it's on the Bitcoin blockchain. It's fun to explain this shortly visually and show that this is stored on a huge amount of computers worldwide and every computer has a copy of your bitcoin.

Ask them how can you get a bank account? (You can't create a bank account) Ask permission and give a lot of personal details. Then ask how to create a Bitcoin wallet. They probably think you create an account somewhere (permission wise) through a middleman. Explain them that you can do it without internet, without a bank, without permission, even with rolling dice. Explain that all your Bitcoin are accessible by a very very big number. And with this number you can create a backup of your bitcoin. To make it readable for us, the backup is in 12 or 24 words.

Ask them who has access to your bank account and what can they do? They can freeze your account. Then ask them what can you do when you have lost your phone with a Bitcoin wallet on it. This is a self-custody wallet. You can restore it with your backup. Show a demo.

Ask them if you can send money to an email address? You can with a lightning address. Give a demo on screen with coinos.io. You can register for free and access your Bitcoin/Lightning wallet in your browser. You automatically get a lightning address. Send money to your lightning address for the WOW effect.

Ask them if you can give someone money digitally with a qrcode and show a demo with Lightning via https://tipcards.io. Send some sats to there with a fun custom message and receive it via Coinos.io.