First of all, Kudos... We need teachers teaching these basics...

As for mining, not even the testnet will do... The last time i looked, the testnet had a difficulty of allmost 226M, wich tells us the hashrate would be somewhere around 1600 Th. An old ASIC won't be good enought to actually solve a block with that difficulty....

As for pool mining: what are they actually learning? They get work from the pool, solve some shares at a very low diff and get some sats in an online account... I'm not sure if they're learning all they can learn from that...

My advice, go for the DOGE or Litecoin testnet, setup a DOGE or Litecoin testnet node, solo mine, actually show them the debug.log and the stdout of their cpu miner, let them chose the address that'll be funded with the coinbase reward...

As for giving them some sats: sure, why not... But you could setup the mining rigs to mine after hours, and stick to mining testnet DOGE/LTC during class hours.

By the way: it might not be a good idear to take pictures of your students holding paper keys... If somebody is able to read the private key, or restore the qr code, they can rob your students, unless you used encryption and a strong passphrase...