The pupil at the school in the city of Lille, identified only as Fouad, took her own life on Wednesday.

Fouad had initially been turned away from the Fenelon school in early December for wearing a skirt, but was later allowed to attend.

The local education authorities have said they were aware of Fouad's desire to transition and were accompanying her in the process. 

There was no immediate explanation for her suicide.

"We're here firstly to honor her memory, to pay tribute to her and to make sure that it doesn't happen again and pupils are listened to," said one of Fouad's friends, Zya.

"The school should have been more tactful, more understanding towards her," she told AFP, though she did not blame the school over Fouad's death.

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Headteacher Paul Marcheville told the pupils at the memorial: "Fouad was fully recognized within the school. She had her place." 

Education Minister Jean-Michel Blanquer said earlier that the government had made  strides in the fighting harassment against LGBT groups.

"But we need to succeed even better in fighting against this," he said.

Anouk Dupont, another friend of Fouad, said there needed to be a wholesale change within society.

"There is a problem within this society which is not the most tolerant, which is quite conformist."

Lille Socialist mayor Martine Aubry said on Twitter that the pupil's death had caused her "deep sadness and great emotion".