Sexual education should be taught separately between male and female youths. If you have boys and girls together in a room learning about sex, that is a recipe for disaster. During class the boys and girls will be distracted by each other, and the knowledge they hear will transform to lust. That will happen regardless, but if females were in the presence of the males during the lesson, the room would turn from a class to a dating agency. Imagination, fits and giggles will replace maturity and seriousness that should be the atmosphere for sexual education.
If you were to separate boys from the girls, the boys will become upset, a clear sign that their original purpose of the class was to mingle with females in a room where sex is the topic.
With the opposite sex absent, the boy will be forced to pay attention to the educational material and will not be exposed so much to sexual drama that is unnecessary at that age. Also, the maturity level of a young child cannot handle the sex class situation with the females around. The teacher for boys should be a man, and the teacher for girls a woman. To not follow this example is to deliberately and knowingly set up a child for sexual conflicts and failures. If one had a truly good intention for sex ed, they would separate the males from the females.