Child labor was the practice of employing children as workers.
During the Occupation of Bajor, child labor was used in Cardassian labor camps on the planet. When Prefect Dukat took over, he abolished child labor as well as other harsh practices. (DS9: "Waltz")
Ferengi also practiced child labor, believing that "Exploitation begins at home". In 2373, Kol was aghast to hear that a Takarian sandal maker did not use his six children (one of whom was only an infant) as employees. (VOY: "False Profits")