Writeacher, I really need your help to rephrase just this part. Thank you very much in advance!
1) Mr. Gradgrind turns his attention to (picks on?) Bitzer, "perhaps because he chanced to sit in the same ray of sunlight which, darting in at one of the bare windows of the intensely white-washed room, irradiated Sissy. For, the boys and girls sat on the face of the inclined plane in two compact bodies, divided up the centre by a narrow interval; and Sissy, being at the corner of a row on the sunny side, came in for the beginning of a sunbeam, of which Bitzer, being at the comer of a row on the other side, a few rows in advance, caught the end. "