I'd be very cautious about assuming that the phrase 'get off me little Indian boy' had a racist intent. I also grew up in a very white area and the only boy in school who was non-white was a Chinese boy. He was very aware of being the only non-white child in school, and he had plenty of friends. If you needed to identify him you would have said 'XXX, you know, the Chinese boy'.
He was probably very aware of being 'the Chinese boy' because it was a nickname that sprang up for him amongst his friendship group. In scuffles, pretend fights, general boyish messing around or games in the playground it was a term that was used and he would grin and retort 'English boy' or similar. It was never (as far as I know) said in malice, it was affectionate.
Racist terms can be used amongst friends (there has been recent research done on this) as a way of reclaiming language. What looks like unfriendly squabbles in the classroom can actually be silly friendship messing about and I would worry that something like that could get taken out of context.
If this boy is Sri Lankan he may well have said that he gets called 'the Indian boy' a lot and how this is wrong and friends may use this as a friendly wind-up term in order to take the sting out of it.
The danger is that when arguments turn 'real' the term can go on to be used perjoratively. To be honest, if they are friends, a card or note to say 'sorry if I upset you' might do the trick.
I think all the 'racist' language stuff is very dangerous, imo, it is far more complex than that.