I assume Thomas the Train is Thomas the Tank Engine ? (sometimes books that sound the same as ours aren't - eg Harry Potter and the Sorcerers Stone confused me for a while because it is not called that here and the words aren't to my mind interchangeable.

Diversion over. If they are then it might be OK if it were one of the originals though still maybe not to his taste. Unless tge teacher is unapproachable it would not be rude or rebellious to just ask if he could bring in a book from home.