What's the meaning of idioms "school in" and "get something into bones"

1. School in: I searched for it on the internet but couldn't find its meaning or anything related to it. I found this idiom in a past year question paper.

2. Get something into bones: I found this idiom in essay "First year at harrow" by Winston Churchill. Here is link to pdf version of essay.

   Thus, I got into my bones the essential structure of the ordinary British sentence -- which is a noble thing.

I inferred from it that he learned the essential structure of english thoroughly, but I couldn't find any such idiom on the internet.

For the record, since no-one answered the other half of the question - when Churchill says that he 'got [the essential structure of the ordinary British sentence] into [his] bones' at Harrow he means that writing good sentences became instinctive with him.