Biology Lesson in Class

During a Biology class, the teacher asked the class:
"Why is that during childhood, gals tend to grow taller than guys?"

A student replied: "That's because guys have "balls" and that weighs them down."

Teacher: "Then why is that at maturity, guys tend to grow taller than gals?"

Student: "That's because gals have breasts and they are heavier than the guy's "balls"

Teacher FAINTED