In Britain, there is a fantastic organisation called Folkworks (linked to the University course in Newcastle).

They run excellent junior/youth/adult summer schools with professional tutors including (in the past) Chris Wood, Andy Cutting, John Dipper, Robert Harbron etc etc.

Sorry, can't find a proper link, but anyone interested should be able to access info from here
http://www.thesagegateshead.org/folkworks/index.aspx

http://www.ourfolkworks.co.uk/ (seems to be a bit out of date, sorry, but thought might be interesting)