At the age of 18, at SFR 30%, is it possible?

Hi to everyone! I often hear from more and more people that they drive with 18 to 30% SFR, with the car of their parents. But now I know that this is not possible, because of the risk increases of the age and that you have to start with at least 140%. How does this end in these exceptional cases? Is this simply not reported to the insurance company and ebi accident pech or are there ways to be insured on so little SFR than the newcomer? Thank you!