Training of the ‘Garzoni’ or apprentices in the Renaissance Masters workshop was far different then one imagines.  The length of the apprenticeship varied and the what they were apprenticing to be also differed.  Not everyone apprenticed to be and artist, many were trained to be ‘artisans’. The apprentices were expected to learn to draw and paint in a classical manner in the style of the workshop master.  The reason is obvious, the works emanating from the workshop required that they look like they are the work of that particular master. They were required to develop a personal style or manner as well so they could become a master and operate their own workshop or ‘Bottega’.  They guilds required each Master to have a unique style, this is the reason we have Michelangelos and Raphaels.  Humanist in the Renaissance revolved around individualism. This is much different than the ‘Atelier’ training that is in vogue today. 

http://www.italianrenaissanceresources.com/units/unit-3/essays/training-and-practice/