Montessori is the ultimate in project based, child-centered learning. But it doesn't mean "the kids have free rein." Rather, it means that each kid has the freedom to choose between a limited set of carefully developed activities, each of which teaches a concrete skill.
On the other hand, it's more friendly than most other forms of education called "child-centered" because it's actually carefully tailored to what's developmentally appropriate for young children.
The problem with a lot of so-called child-centered instruction is that it's not centered on actual children, but on some hazy, over-romanticized, Rousseau-like ideal of what a 'child' ought to be.
What I see all the time is that schools have somehow managed to do the exact opposite; they choose the worst of all worlds. They take the authoritarian approach of bad traditional practice and wed it to the fuzzy curricula of bad progressive practice. The result is the mess we have today.