In my experience, when I call on a girl to answer a question, there is a higher chance that a boy will blurt out the answer when the girl does not answer immediately. Also, in my experience, when we read aloud, boys heckle the girls at a greater rate than boys heckling other boys. There is no easy solution to this but I have had some success in equalizing participation.
In the beginning of the year, when I ask a girl to answer a question and a boy shouts out the answer, I make it clear that a: I appreciate it when students participate in class. b: when I call on a student I expect that student to have a chance to answer the question and not be rescued by a boy. There have been times when I call a boy into the hall and have a quick talk with him (about 1 or 2 sentences). The boys don't mean any harm; it's basically a mating ritual like throwing paper balls at them. Just be aware that it is going on and try to put a stop to it. I certainly protect my girls, but it's just one issue among a million to deal with.
