Yep, definitely a combo. We know a kid who at 16 got a prestigious job over the Summer working for a very amazing research group. He got it himself. He applied and was picked from many. The rest of the kids we know got jobs via connections ( parents mostly). A couple through school programs or by competitive application ( seems the best way). Most of the parentally involved internships had very little knowledge transfer.
My kid got an internship via school. They offered it to the top two kids in a particular subject. It was paid and my kid realized that environment wasn’t a likely career. Good to know. I’d imagine that some schools have companies contact them and ask for interns and teachers make recommendations.