Medical journal reports UK also ranks near top of high-income nations for teen drinking
London Britain has the third-highest proportion of teenagers who are sexually active at an early age.
It also ranks badly among high-income nations for harmful teenage drinking, according to a series of studies published in the Lancet medical journal on Tuesday.
The research, plus a report by Unicef, call for more attention to be paid to the changing needs of the young, warning they are at risk of mental and physical illness and that too many will die early.
Neglect
The studies found neglect across the globe, including in affluent countries such as Britain and the US.
Among 40 countries with broadly comparable data, England had the fourth-highest number of adolescents who had been drunk by the age of 13.
Wales came fifth and Scotland eighth. Wales had the third-highest number of 15-year-olds who drank every week, with England fourth and Scotland again eighth.
Crucial role
This generation is unlike those that have gone before, say Professor Susan Sawyer and Professor George Patton from the Murdoch children's research institute in Australia.
The Arab Spring showed the crucial role of the young as agents of social change, but they are vulnerable, says the paper.
"Young people were at the forefront of the social unrest across north Africa and the Middle East that began in Tunisia in December, 2010.
Serious threats to health
"Although many succeeded in toppling the restrictive regimes that they fought against, they faced serious threats to their lives and health.
"It raises concerns about the extent of young people's exposure to violence, exploitation and abuse, and suggests the need for greater protection of human rights," write the authors.