Channel One News is a youth marketing company. The company exists for one main purpose: to bring commercial messages to hard to reach teen and preteen students.
“Lightest viewers” means students who don’t watch much TV at home. “Lightest viewers” usually means good students with their priorities in the right place. “Lightest viewers” are students whose parents may restrict TV viewing during the school week. Channel One is telling potential advertisers that ads on their in-class TV show get around these foolish parents with their asinine viewing restrictions. Kids have to watch Channel One’s commercials. That’s a powerful inducement for companies who have something to sell young people.