We can hire apprentices, we cannot keep them past year two

We can hire apprentices. We cannot keep them past year two.

The ones who leave don't go to other shops. They leave the trade. Best guess is they can't see the path from where they are to where the senior guys are, and four years feels like forever at 22.

Anyone cracked this? Specifically interested in months 6 through 18, because that's where we lose them.

Electrical side here, but I'd guess this isn't just us.