Janie started spending almost all her free time with her boyfriend; her peers complained that "those two are joined at the hip". Her attendance suddenly deteriorated and, when she was in lessons, she was pale and easily distracted.
That was when I realised something was wrong. I tried to approach her, but she refused to talk. Was I worrying over nothing? I could hardly ask outright if she was pregnant. What if I was wrong? All her form tutor and I could do was keep an eye on her, try to get her to talk, and be there if she needed us.
She had, it turned out, known for weeks she was pregnant but had carried on in silence, perhaps kidding herself that the problem would vanish. Odd, I know, but how many of us work with students who try to blank out forthcoming exams? Janie was only doing in an extreme form what plenty of people do when faced with unpleasant truths.
By now, it was too late for the morning-after pill, so Janie had three choices - abortion, giving up her baby for adoption or teenage motherhood. And yet many schools and colleges avoid displaying information about this pill, arguing that it condones under-age sex. They argue that it is better to provide information discreetly, when students "find themselves needing it".
But Janie is precisely the sort of girl who would have benefited from easier access to emergency contraception. She was not the streetwise, uninhibited type who could stride confidently into her nearest clinic, get all the info, ask questions and pick up a few pill.
Janie had been too scared to see her own doctor, let alone visit a clinic. School was the only place where she had any hope of finding a way out. Students need access to information in the familiar environment of their own school, talking to health professionals and teachers they know and trust.
Janie did eventually tell us she was pregnant. We did what we could to help, which by this time was very little. Her parents were incredibly supportive. After much discussion, she decided to have an abortion. I found this upsetting, but understandable. What upset me most was the knowledge that four tablets could have prevented it. She missed some schoolwork, but we did our best to help her catch up.
When she did come back, she was withdrawn and preoccupied and her exam results were lower than we'd expected. On a more positive note, she made a full recovery, completed her courses, and secured a traineeship. But she'll probably always wonder whether she could have done better for herself had her circumstances been different.
Only by giving clear, carefully worded information to youngsters to help them make their own choices can we hope to reduce Britain's high number of teenage pregnancies.
There are many issues surrounding emergency contraception: does it flout a school's religious ethos; do you involve parents; what about confidentiality? What would you do if an 18-year-old told you she was taking the morning-after pill and asked you not to phone her parents if she missed school the next day? Whose rights come first - the student's or the parents'? It is something every teacher should consider. There could be a girl who has just taken the morning-after pill in your next lesson, in your school. And she may not have a clue what's happening to her. Would you want to know about it or not?
The writer, who wishes to remain anonymous, teaches in central England