Hi,
usually there is support for kids who do not speak the language. There are reception classes or special intensive laguage classes usually organised by the state schools
On the Canton of Berne website this is also suggested..Is the problem due to the fact that you are only short term. I would explore it further with the cantonal education authorities.
http://www.erz.be.ch/site/fr/sls-vol...n-francais.pdf
sorry it only appears to be in French or German