There is no guarantee that those pupils who are expelled will ever go to state school again under the tough new legislation, which, although supported by teachers in the Vaud, came out of the blue.
"We need to protect ourselves," explained Alain Gillieron, a Lausanne teacher and regional representative of the centre-ground Radical Party.
"Right now the worst-case children are excluded from school and transferred to specialised institutions. But then they get themselves excluded from these as well, which means they go back to normal school.
"We can't go on like this forever. It's not fair on the other students."
But the move has been censured by parents' groups and could now be challenged in the courts.
"We can't understand it," said the president of the Vaudois parents' association, Michele Laird. "It's a short-term solution. Once outside the social system, the child risks falling into even worse trouble, which in turn needs sorting out later."
Philippe Huser, president of the country's Youth Tribunal, is also worried. "It's true that sometimes it's difficult to find an institution adapted to the unique needs of a specific child. But the law shouldn't condone a dead-end situation," he said.
The newspaper Le Matin has already reported that the decision might be contested in the courts. A further cause for concern is Switzerland's status as a signatory to the International Convention on the Rights of the Child, which might look unfavourably on this type of sanction.
Criteria for exclusion include violence, endangering others, and disruptive behaviour, and the more extreme cases usually involve adolescents between the ages of 13 and 16. However, a pupil as young as 11 was recently excluded from a Vaudois school. Definitive exclusion normally involves only five or six children a year.
In the 25 other cantons, the law is more flexible. In some of them definitive exclusion is possible, but a placement elsewhere is guaranteed. In others, such as Geneva, exclusion can only be temporary, and the teachers are expected to try to integrate even the most difficult children back into the mainstream.