Definitely not leghorns - legs are too thick. I would guess white rock or cornish cross. If it's white rock, they can be pets and lay eggs. If it is cornish cross, they will flip (drop over with heart attack eventually). We kept one pullet from a meat bird batch one year and she lived to 7 months old, just started laying eggs and flipped. They are not meant to be grown long term. They are usually butchered between 6-8 weeks old. Yours look kind of small for 6-8 week old cornish cross tho, so not 100% sure. Ours are that size and only 3 weeks old.
Jody
Jody