Yes, you should be using the scoreboard to mold the behavior of even one or two in the room. Without pointing out who the offending party is/parties are, give a general explanation after marking a frownie, such as, 'Some people forgot rule 1 which says...' The power of peer pressure should kick in so that the ones who were the offending parties 'get it' and want to do better next time. By the same token, if you 'need' to find a positive, find a student/students who are doing something well and award the class a smiley to reinforce that behavior/work habit. Make sense?
HTH!
Joni