A few years ago, when Mae Gayle Dalton was in the 9th grade, her close friend was sexually assaulted by a former boyfriend on school grounds. Making matters worse, Dalton said, school administrators punished her friend more severely than the boy. Fueled with rage, Dalton gave herself a crash course on sexual assault and the cultural forces that sometimes encourage it. And this year, as part of a Girl Scout project, she took on the task of educating her Danville, Virginia, community about what she learned.

Armed with buttons and flyers, Dalton, now a high school senior, has been camping out at local fairs, Rotary Club meetings and school board sessions, giving speeches about her cause. And she's been pushing her state representative to support legislation that would require Virginia's public schools to teach "yes means yes" as a standard for sexual consent.

The usual approach, which relies on teaching kids that "no means no," isn't enough, Dalton said. Often, when it comes to sexual activity, she said, "there is a fine line. We have to un-blur it."

Some states agree with her. In 2015, California became the first state to require that public schools teach students what’s known as the affirmative consent standard, which requires a clear, unambiguous and voluntary agreement to participate in a specific sexual activity.

Last month, Virginia Gov. Terry McAuliffe, a Democrat, signed a law that requires public middle and high schools to teach age-appropriate ways to prevent dating violence, domestic abuse, sexual harassment and sexual violence. (Dalton says the law doesn't go far enough because it doesn’t specifically require that "yes means yes" be taught.)

Also in March, the Maryland House of Delegates approved a measure that would require public schools to teach the "yes means yes" standard for sexual consent. (The Maryland Senate failed to advance the bill this week, effectively killing it for this year.) Similar bills have been introduced this year in Illinois and Pennsylvania. And in February, the Nevada Youth Legislature, which has the power to pitch youth-oriented legislation to the state Legislature, introduced a bill that would, among other things, require public schools to teach students about affirmative consent.

The "yes means yes" measures don’t change the legal definition of sexual assault. They vary from state to state, but generally, "no means no" remains the legal standard for prosecuting sexual assault cases.