Sun Education has never made this information publicly visible. However it is easy to be mislead by reading public forums like JavaRanch that not many people fail. I suspect that quite a lot of people do fail, even those who have experience programming Java, but many people are reluctant to announce such an event in public.
You're right. Not many people here announce that they have failed (some do and share their experience, things to do...). I don't know why Sun does not publish this. I've really been wondering how tough this really was.