Complex sentence: He graduated in 1891 and from 1891-92 was an Assistant Master at Blair Lodge School in Polmont, Scotland, as he was at Tonbridge School (where he studied as a boy) from 1892-1923.
Split into simpler sentences: He graduated in 1891 and from 1891-92 was an Assistant Master at Blair Lodge School in Polmont, Scotland. At was at Tonbridge School, where he studied as a boy, from 1892-1923.