Educated at Eton at a time when England was in a ferment of religious revivalism, Hogg took a position in a tea business in a poor section of London and was moved to sympathy for the waifs playing in nearby streets. In an effort to obtain firsthand experience with the problems of lower-class children, he disguised himself as a shoeblack and worked nights alongside these boys. His attempt to teach reading, with the Bible as a textbook, to two crossing sweepers led to the opening of his “ragged school” in Of Alley, Charing Cross. The school was moved to Castle Street in 1868. By means of trade classes and a combination of education and religious work, Hogg hoped to reconstruct the lives of destitute children.

In 1878 Hogg set up his Working Lads' Institute at Long Acre. Three years later he acquired a run-down building in Regent Street known as the Polytechnic, which he repaired and converted to “the instruction of artisans and clerks in the principles and, to some extent, the practice of their breadwinning pursuits.” His work was carried on without public funds until 1889, when it won the support of the London County Council, and within four years other branches of the Polytechnic were established.