John Witvliet, writing about worship in Calvin's Geneva, writes:
But in the Reformation era, the entire congregation sang— men, women, and children together— an innovation in an era in which women’s voices could otherwise be heard in worship only in a convent. The children, for their part, were the leaders of the song. In the 1537 Articles, Calvin instructed:
This manner of proceeding seemed especially good to us, that children, who beforehand have practiced some modest church song, sing in a loud distinct voice, the people listening with all attention and following heartily what is sung with the mouth, till all become accustomed to sing communally.
This practice must have continued, for in 1561, the city council mandated that new psalm tunes not be used until they were taught to the congregation by the school children. Although Calvin argued against a distinction between congregation and choir, he did allow children to serve as the precentors of the people.
Witvliet, John D. (2003-07-01). Worship Seeking Understanding: Windows into Christian Practice (Kindle Locations 3130-3140). Baker Publishing Group. Kindle Edition.