Nursery paint stains

So we have a set of clothes only for nursery which I’m prepared might get ruined. However, recently they’ve done some painting outdoors and his overalls are ruined by the paint. The stains don’t even fade in the wash. We only have one warm and one thinner overall for him, and even second hand they’re not super cheap. Am I wrong to be annoyed by this?? We paint a lot at home with water based paints and they all come out in the wash. So what on earth are they using?!