A breaker boy was a coal-mining worker in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 and United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 whose job was to separate impurities from coal

Coal

Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 by hand in a coal breaker

Coal breaker

A coal breaker was a coal processing plant which broke coal into various useful sizes. Coal breakers also removed impurities from the coal and deposited them into a culm dump...

. Although breaker boys were primarily children, elderly coal miners who could no longer work in the mines because of age, disease, or accident were also sometimes employed as breaker boys. The use of breaker boys began in the mid-1860s. Although public disapproval of the employment of children as breaker boys existed by the mid-1880s, the practice did not end until the 1920s.
The first function of a coal breaker is to break coal into pieces and sort these pieces into categories of nearly uniform size, a process known as breaking.