School of the Cat managed to successfully get to a point where 1/10 women survived. School of Crane is the later iteration of the School of Cat, which is why I mentioned them specifically.

Where is this info from? I could only find fan fiction so far.

As for why, it’s because Ciri wants to be a proper Witcher like Geralt.

Too thin for a 70% death rate when you already have most of what it takes for other reasons.