The unnamed teacher handed out a homework note to pupils of the collège Antoine-Delafont, a secondary school in Montmoreau-Saint-Cybard southwestern France.
It read: "You've just turned 18 and have decided to end your life. Your decision appears irrevocable. As a final effort, you decide to explain the reasons for your act.
"In setting out your self-portrait, you describe all the disgust you feel for yourself. Your text must bring up certain events in your life at the root of this feeling."
A group of shocked parents wrote an anonymous note to the headmaster and local school authority, saying: "We are horrified that this type of topic should be proposed to children between 13 and 14 years old."
One parent, Béatrice Goupilleau, told Le Charente Libre, the local newspaper, that her son was embarrassed to let her see his suicide note and the teacher's comment, which read: "Not precise enough."
"Thank goodness for that!," she exclaimed.
Another, Hélène Ferrari, said: "What shocks me is linking autobiography with suicide, it's really over the top."
Christophe Clément, president of the FCPE parents' union in Montmoreau, said such a subject is "practically inciting (pupils) to commit suicide."
Jean-Marie Renault, the local education authority head, said the teacher had been officially notified of his suspension, adding: "Telling a pupil that he is about to end his life and that he must recount it appears troubling to us."
His local authority has had to cope with two pupil suicides in recent months.
Geneviève Fioraso, France's higher education minister, waded in, saying: "If the topic was launched in this way, without accompaniment, without context, it's dangerous."
But as the media storm around the suspension grew, many colleagues, parents and pupils rallied behind the teacher.
One pupil, Lola, said: "He's our favourite teacher, the best we've ever had in this school. We don't want him to be punished."
Villagers were generally supportive, with one young mother telling Charente Libre: "What do you think they talk about in the playground? The images they see on TV are far more shocking."
"Suicide is part of daily life. Perhaps the teacher wished to raise their awareness of the issue," said another.
By Tuesday afternoon, an umbrella group of parents issued a statement calling for the teacher's "immediate return to his post for the good of our children". Pupils and teachers "appreciate the qualities of this teacher," they said.
Media coverage of the affair had been "over the top and inappropriate", they added, noting that the subject had "not shocked" pupils at it had been "well presented" by the teacher.
The local SUD-Education union said the suspension was a "bad response taken in haste under pressure from a part of public opinion".
Commenting on NouvelObs website, French teacher Yves Delaie said the affair highlighted a huge problem with post-1968 teaching in France, namely "Wanting at all costs the pupil to talk about himself."