I’m Asian, so a slightly more acceptable shade of brown, I don’t have typically Asian features (such as the nose), so when I don’t have a tan I simply look Italian/Spanish and get treated like a caucasian person.
At primary school I was regularly called Paki, darkie etc, all words that a child would have to be taught by their parents, not things like brown or even dirty that a child may observe. In year 5 so when I was 9/10 a song was going round the playground that song went like this “Hey Pakistani does your granny have a fanny? Does it smell? (Make a sniffing sound) Fucking Hell”. This would be sung at me, in full hearing of teachers and dinner ladies, not a single one ever said anything and no one was punished. I did tell a teacher what had happened and I was told off for being silly because songs are fun.
My siblings and I were the only non-white children at our school. Staff would become angry if we shared our food with our friends as it was apparently Indian stuff and you don’t want to touch that. I’m still not entirely sure what makes a packet of pom bears indian 🤷🏽♂️
It was a fairly small primary school so PE was sometimes done as a keystage, when my brother and I were in the same keystage we would be split between the two teams because the teacher who led PE thought it was only fair that “both teams have to have one”.
I was very rarely represented in story books or textbooks, then when I hit year six our examplar papers for SATs would sometimes have people with Asian names in (but only maths problems obviously 
), my year 6 teacher would go to great lengths to pronounce these in absurd ways while the rest of the class stared at me. Even my friends, after all it is hard for a small child to go against authority.
I couldn’t go to most of my friends houses because they had racist parents, if a friend came to our house their parents would always ask several times if they would be made to eat curry.
Secondary school was harder, you’re much more aware. Again, a very white school, but alongside us there were two Chinese children.
Racism was much more direct here, students would call me the N word, make monkey sounds, throw bananas at me, call me a terrorist, shout 9/11 at me. It was an everyday thing. But at secondary there were at least some teachers who tried, my PE and science teachers were really nice.
In English we were studying a peom in year 9 called The Little Black Boy by Blake, guess who was forced to read it out aloud in class and then sit through two lessons of people giving examples as to why white people are better with the teacher nodding in agreement.
There was a spate of vandalism in the toilets, school used to deal with this by taking me and the Chinese boy aside and teaching us how to use a Western toilet.
If something went missing in class the teacher would do bag searches. There was one teacher in particular who taught history. If something went missing he would search by bag and upon not finding the missing item he would declare that the person must have left it elsewhere. In a class of 29 white children very few will actually be racist, but they were being taught by a trusted authority figure that people who aren’t white are thieves.
I’m a rugby player, now rugby isn’t as bad for racism as football. But I would be called a monkey or have players (or sometimes parents watching) make money noises. My PE teacher was very good, if he witnessed it happening he would always have the game halted and announce why. Because of him I had to confidence to go on and play rugby professionally and I still do. I learned later as an adult that he was punished by the school for speaking out about racism.
Outside of school was hard, when your brown or black and male you’re criminalised from a very young age, I would be asked to wait outside shops, my friends wouldn’t, I would be refused entry into the cinema, my friends wouldn’t. I was a teen just before mobile phones became hugely popular (I’m 32). We sometimes met up in town on a Saturday, we would agree a place and a time. I soon learned to turn up a bit late so at least one friend was already there, if I waited alone I would be moved along by the shopping centre security, a white friend waiting alone was never moved along.
Stop and search has been a normal part of my life since the age of 15.
Everyone has unconscious bias, including me. But that is completely different to racism, racism, like sexism or homophobia is an active choice.