Such acts of vandalism are becoming increasingly commonplace in France.
A statue of Christ was even recently found in a garbage dump.
Attacks on Catholics have been increasingly aggressive in the past few years in Spain and often go unpunished.
The catholic school group Jean Paul II has around 500 pupils in Forez.
The degradation occurred precisely eleven years after Mohammed Merah's mass shooting at a Jewish school.
The Leimen police station has started the investigation and is looking for witnesses in this connection.
Security has been deployed to the sites of the most recent attacks after ten Christians were found killed by the militants.
Church vandalism remains too often unpunished across Germany.
A police source told AFP that a priest was also injured.