Research Internships in high school?

How prestigious is it to have done a research internship at a university over the summer during high school? A lot of kids at my school do them, and the pressure for internships are high, but is it really an important factor when it comes to college admissions?

My son did research and wrote a paper that was accepted into a conference. He traveled abroad to present his research. He did not get into his first choice school. He did get into all the other schools he applied to and received great merit awards. His research was not enough to tip the scales in his favor at his top choice, but I’m confident it contributed to some of his merit money as indicated by admissions at a few schools.