The Daily Mail reports that Wendy Maguire, 16, was "fed alcohol by other pupils" at Palmer Catholic Academy in Ilford, East London, and had been "put in the sick room after collapsing twice in the playground".
However, by the time her mum, Leila, 49, had arrived at school to collect her, she had been allowed to walk off the premises unaccompanied. The teenager was later found dead by the busy A12 after falling from a footbridge.
Her heartbroken mum told reporters: "Wendy was confident, popular and smart. She dreamed of becoming an accountant and was looking forward to going to university.
"This was not a girl who would take her own life. We've been told her classmates pressured her into drinking alcohol and wouldn't let her stop. The teachers knew she wasn't herself so why was she allowed to leave school? She should have been properly supervised until we arrived."
It is reported that Wendy - an A grade student - had begun drinking on the Friday morning before going into her classes.
Passer-by Saidaa Shariff who saw the teenager in the road told the Daily Express: "The image of that poor girl will haunt me forever."
Friends and family have since laid flowers at the scene and left messages of condolence on Facebook.
What a tragic story.