A 14-year-old girl cannot give "informed consent" to sex.
No matter HOW much "sex education" she may have had. In the classroom or under the bleachers.
This says far more about the nature of today's "informed" than the age in question. 14 year olds have been perfectly informed of the consequences of sex for centuries, merely by living on farms and in single room dwellings. It is the modern penchant for insulating people from the consequences of their behaviors that has extended adolescence.