What were your criteria for trading at school?

I was a kid in ‘99 during the original Pokémon hype and we used to trade based on HP and occasionally on attack scores. It wasn’t necessarily 1:1 but a Charizard (120) was worth only slightly more than a Zapdos (90) - contrary to contemporary prices. How did you decide to make your trades because when you’re 10, you’re not thinking of the cash value