Complex sentence: Blacks came in later (many of the men were Pullman car porters and other railroad workers); schoolroom photos from 1909 and 1911 show two or three black faces among the 30 or so children pictured.
Split into simpler sentences: Blacks came in later and many of the men were Pullman car porters and other railroad workers. Schoolroom photos from 1909 and 1911 show only two or three black faces among the 30 or so children pictured.