I can see why you're worried if he has to take public transport and never has before. I grew up in small, rural town and never took any type of public transport until I was in Uni and all my friends had to show me how it was done. Took me a long time before I felt comfortable enough on my own. I would have been terrified at the age of 14 of moving to a brand new country and having to do so on my own. I was not an adventurous kid at all. Very shy. Heck, we have so many grown up people who come onto this site terrified of having to take the bus and how to do it. So I think your fears are justified!
I think it sounds like a good plan to take the bus/train with him around when you first move, just so you can get used to and he can feel comfortable. Even if its just to the shops or whatever and not to school.
If its walking, you could just walk it together at somepoint before school starts, if he'll walk with his mom
but in that case, you could not make a big deal about, but rather, once you first move, "Oh, let's walk to the school so that we all know where it is"
Good luck with your move!!