From the introduction to Keith Douglas: The Complete Poems:

"The masters at his first school found him difficult: 'bumptious and aggresive', too bitingly critical, too unorthodox, too fond of his own fantastic methods, too clever for his own good. His next school, Christ's Hospital, only managed to contain him by being exceptionally forgiving and flexible. His biography helps us to understand this. His whole childhood can be seen both as a nursery for his peculiar alienation, or what he called his 'long pain', and as a forcing house for the unusual strain of independence in his character. He pondered this a good deal, partly because he could see how much dislike it provoked. From quite an early age he showed an acute awareness of somehow having to manage inside himself some extra thing that was almost unmanageable."