OMG it's WRONG. Legally, and emotionally and perhaps physically.
And I'll tell you why.
Legally - The law provides an age where a person is legally responsible for their choices. That means they understand the event and the possible ramifications, both short term and long term, and make a decision based on that.
Physically - well assuming she has had sex before, how responsible has she been? Let's face it, a woman who persues a minor is not acting responsibly. What are the chances of STDs or pregnancy?
Emotionally - Well yup the boy can strut in front of his friends. Or can he? Does she want him strutting his stuff? Telling all the friends? She knows what she is doing will get her into trouble. So I suspect there is an element of secrecy to this "relationship". So he can't tell. If wants more he has to keep his mouth shut. Hmmmmm Can you think of how this might affect him? It is hard enough to keep the secret you scored with your same age girlfriend.
What about experience? What happens to a 14 yr old boy who is expected to "perform" for a woman with experience. Does he know how? What does it do to his self-esteem to be told how to do it or be shown. Yea there is the payoff but what emotions lead to that? And then the fear after of "Did I do it right?" So here he is in the student role - again.
What happens if he does get an infection or she gets pregnant? How does this kid explain: I got my teacher pregnant or I got my STD from the teacher.
So here he is - isolated. he can't hang out with kids his age because she is monopolizing his time. He doesn't talk to people because he might let out the secret.
When it's all over and she is tired of him - what then? How "used" will he feel when he sees her move on to a new conquest? How bad is he going to feel when to get rid of him she puts him down or his "love-making" skills?
And once it is over how does he get back to "normal" adoloescent development and learn to relate to girls his own age? Will he expect them to teach him also? Or perhaps he now has too much information and can't relate to girls who want to growe up normally? Will he seek out other older women/girls? How does this sexual fantasy turned into reality affect his future sexual fantasies? And future ability to perform wil people his own age?
I'm sure I could think up more if I hang out here but I am shocked by the opinions of some people. Yes the moment will feel good. But those "moments" are pretty small in the grand scheme of life.
All that and one more: What is all this attention doing to him now? How will it affect him in the future. How do you go from all of this to trying to find a wife and explain "I was the kid who..."