^I don't know any of this to be absolutely true or false. But this is the best, most educated guess I have to offer re: Casiraghi edu: (excluding pre-secondary level)
Andrea
1) International School of Paris: 1999-2003 (having had to take the IB twice)
2) McGill University: 2003/2004 (at least semester term there, maybe two, i.e. Fall 2003 through Spring 2004)
3) AUP: Fall 2004 through Spring 2007 (my theory puts him getting his Bachelor's in 2007)
4) The New School: Fall 2008/Spring 2009
5) Started internship @ embassy: September 2009 (probably was just a one-year internship, and might have been part of his thesis @ TNS)
Charlotte
1) Lycée François Couperin, Fontainebleau (2001-2004)
2) CPGE/hypokhâgne-khâgne course @ Lycée Fenelon, Paris (2004-2006)
3) Third year toward License of Philosophy from Sorbonne IV: 2006-2007 (the two years @ Fenelon counted as the first two, and it's a three-year degree)
4) 2007-2008: Two internships (publishing house of Pierre Laffont, Paris & The Independent on Sunday magazine in London)
Pierre
1) Lycée François Couperin, Fontainebleau (2002-2005)
2) Gap year (I believe he took one) 2005-2006
3) Bocconi University, Milan: Started in September 2006
4) 2006-2007, 2007-2008, 2008-2009 (the degree he was going for was for three years, but supposedly, if the tabloids and gossips from inside his university can be trusted, he failed exams at least once, maybe twice and had to repeat a lot of work)
5) He signed the papers to assume majority shares of Engeco S.A.-Monaco: June 2009