The tween entering middle school is morphing on every level -- physically, emotionally, cognitively. "Most girls reach puberty by age 12, and the first signs -- weight gain and pimples -- are often unwelcome," says Juvonen. "Whereas for boys, the changes -- deeper voices, muscles, facial hair -- are more desired attributes." Both, however, have a tough time navigating the social pitfalls of adolescence. Boys feel pressured to establish themselves as powerful and popular, yet many also end up feeling isolated. Girls get competitive in a different way. "When one develops breasts sooner than her friend, fissures emerge," says Rosalind Wiseman, teen expert and Family Circle contributing editor. "Will she flaunt her new body or become boy crazy? Will the other one mimic her friend or feel alienated? These differences can upend long-standing relationships."
Cognitively, adolescents are making great leaps forward. "They're stretching their reasoning skills and are capable of more nuanced thought and self-reflection," says Juvonen. Ironically, this also explains why they're so emotionally volatile about their peers. Everyday worries get blown up into anxiety-provoking incidents, and it becomes even more difficult to concentrate on learning.
When Tess Henry, 13, started seventh grade in New York City, she was separated from two longtime friends, and they drifted apart. She began hanging out with a new classmate. "She'd be nice one day, a real mean girl the next," says Tess. "No one ever treated me like that before." Her grades suffered, she stopped doing homework and some days refused to attend class. Her parents asked a school counselor for help, and Tess soon parted ways with her so-called pal. Now in eighth grade, she's rebounded and is back together with her old buddies. "They're good friends, plus they're really smart, so I want to keep up with them," she says.