trace your ancestor's childhood, then it's a good idea to check what the school leaving age was at the date you are interested in, because that will determine whether you should look for school records such as registers, or employment records, e.g. wage books.
But there may be a period of overlap because children who reached a set educational standard were allowed to work part-time, and you may find school exemption certificates (above) amongst family papers or in local archives.
You may be surprised how young your ancestor was when they began full-time work; the 1918 Education Act raised the school leaving age from 12 to 14. As late as 1861, although the minimum age of starting work in a coal mine was nominally age twelve, ten- to twelve-year-old lads were permitted to work underground if they had a school certificate to prove that they had reached a sufficiently high standard of literacy.
Section of a school exemption certificate dated 4 April 1894 permitting a Manchester schoolchild to work one day per week.
Girl with slate and schoolbook. Early twentieth century postcard. Author’s collection.
Collier’s phthisis. A Manchester doctor’s sketch of ‘black lung’ from a 65 year old collier. Reports of the Factory Inspectors, 31 October 1871.