Aaanyway, if you wanted to reveal my place of origin you probably could, given how you're fond of digging through my post history. Go see if you can put together the clues. Or don't, because if I did want to share that I would have at this point, don't you think?
So basically what you're saying is that you're North American and haven't had any education outside of North America, yet you're trying to make it sound like you have so you can pretend you have any experience to disprove anything others say about non-western education systems. Because there is absolutely 0 possible way to pin a person's place of origin down based on the continents they went to school in unless they're Australian or something. That answers all the questions I need to know about.
Your argument basically boils down to "you're making generalizations and assuming other countries' education systems are just like the US'!" while making the assumption that other education systems are completely fundamentally different to the US' and have no similarities (which it's pretty easy to find out that most other countries do use the same general scale for grading and do have a massive problem with ableism especially with neurodivergent kids). And making crazy comments about how saying other countries have a problem with grading systems and ableism = ethnocentrism? Like you have provided absolutely 0 counterexamples other than vaguely saying "I know people who aren't American" without any specificity which is pretty sus. Do you just assume the entire developing & underdeveloped world has to be "backwards" from the US or something? That would seem pretty ethnocentrist.
If your counterexample is that in multiple of the countries you went to school in the education system didn't work like that, the obvious point is going to be "where was it that education didn't work like that?". I would hope you'd realize that before you even brought up your own location to make a point in the first place.
