Three Portland high school students are reinventing sex ed    {A shorter version of this story appeared in the September issue of Portland Monthly .} When 18-year-old twins Milena and Sofia Ben-Zaken and their friend Tess Waxman, also 18, were at Sunnyside Environmental School, their sex ed instruction was laughably brief. "We had one day on puberty in the 5th grade," Milena recalls. “We didn’t really have sex ed in 8th grade, either, except for on the 8th grade retreat,” Sof