I think a lot of young people (particularly boys) drive recklessly when they first start. The freedom goes to your head, you want to be out on the roads, and at night you think you can get away with driving as fast as you want because there aren't many people around - they're still too young to realise they're not invincible.
Stopping them driving at night wouldn't work. What about if they have jobs, or need to visit sick family members, or have another kind of emergency?
I think - and I've always said this - that drivers should have a black box for the first year after passing, and should only be allowed to take it out if they have been shown to have driven sensibly. Really, everyone should have one, as it would help keep premiums down for those who do drive properly, but I know that's not practical. I also think everyone should go on a speed awareness course as a part of their driving theory, because so many people I know have said they're eye opening. I haven't been on one myself (I try to keep to sensible speeds, but that doesn't mean I'm always perfect) but they say they don't speed after being on the course, so that could be a good idea.