School?

Four months later, and I still don't understand the university system in France. I've got the basics down the "fac"s (normal universities, practically free, universal admittance) and the "grands-ecoles" (elite, specialized schools, Science-Po is also included in this, kind of).
But I still don't quite understand how the greve/blockage was able to last nearly the entire semester. It wasn't all universities, in Nancy it was just the fac de lettres (humanities campus). None the less, it lasted the entire semester, finally neccistating an administrative closure of the school. That was supposed to last all the way until september, with the students losing their semester, but suddenly the fac re-opened this week. The semester is now extended until the end of June so that the students don't lose their semester.
I don't quite understand how a minority of students could completely shut down the university like this, but the authorities could never send in police force against the students, because it would then become an increased problem of students against "the man".
The real problem lays in the nature of the university. While sky-rocketing university prices in the states are completely ridiculous, I think free university in France causes an equally large problem. Without threat of financial pain, there's little incentive to succeed in university. I learned today that 40% of university students (that is the public universities, not the grands-ecoles) fail and have to repeat their first year. There are numerous students who fail but stay in school because its a (relatively) easy lifestyle. My host sister is a perfect example of this. She was 15 days away from quitting a degree when she quit the program and started another. She's now finished, but has decided that she wants to stay in school for another year, just because she doesn't want to get a job. (well, that's the way my host mom tells it anyway). All in all, the French academic system is one that allows top students to succeed, but leaves less motivated/talented students treading water. This is one of the main reasons that students put up with semester long greves. In the states where university can cost up to 30,000-50,000 a year, students feel the push to get through their studies quickly and put some effort into it.