I had an ex-partner who was white passing but half-latino, brought up in a very white part of the UK. It was very clear his experiences still really bothered him in his 20s, and there were a lot of experiences of "othering" as he grew up from both adults and children. It wasn't overt racism, but he was very aware of e.g. teachers mentioning his heritage almost randomly to visitors, or if he ever had any success his heritage was brought up even if it was irrelevant.
There's also the issue of people talking about "immigrants" etc in a racist way, and him knowing they were talking about his mother. And obviously people would say, well, you should call that out. But you have to consider the potential threat of violence (In the same area, around the same time period, a friend of mine who is pakistani was attacked outside a pub, for example)., and, often, in a school classroom being told off for expressing outrage. He experienced teachers trying to "both sides" race issues and make it into a debate when he was at school.
There's also the issue of having to explain yourself and your culture to people all the time. "My first language is Spanish", "But you aren't from Spain?" "No" "So why do they speak Spanish in South America?".
And yes, as a teacher, some teachers are 100% still racist- some overtly e.g. I've known teachers who use the work "p*key" as an insult about students (both travellers and non-travellers). But equally you get teachers who will defend their right to read the n word aloud, even if it makes the only black kid in the class really uncomfortable.
If you have an entirely white teaching body, it can be hard for mixed race/ethnic minority students to explain why an incident upset them, and some staff won't get it. And I don't think it's the same as tensions between different ethnic groups. I'm not saying it's never a problem, but it's a different problem. And you'd still not be in the position of being the only person experiencing it.