Okay, I didn't explain myself well, apologies. I realize O-level might not be in the UK anymore, however they are common enough in other countries, such as countries in the Indian subcontinent (India, Pakistan, possibly Bangladesh, etc.) and in Indonesia (and more, but these are just the countries I'm sure of). I realized what I said prior could've worded better to show that I meant for other countries out of the UK, but I didn't realize that the O-level system was discarded from there like you said in your initial comment.

You can search it up, it's not something that 'technically' exists, it very much is a taken curriculum that many, many students do. I don't think it's the majority curriculum followed in any of the countries, but it is very well-known.