It is not about immigrants in general.
Chinese or koreans will rape any european pupil at any test possible.
It is not about whether the immigrant is poor or not.
It is about the culture, and the choices made by the specific immigrant and his parents.
I 100% agree it's to be expected. For multiple reasons; language barrier, differing earlier education, differing educational culture, those are the easy ones. The obviously less talked about issues are some of the children don't have parents anymore, they are all likely emotionally scarred from where they came from, not to mention the climate of distrust that surrounds them.
People from poor war-torn areas with bad education do worse at furthering education? It's almost like there's some kind of study on how important educating children in their formative years is or something! Who woulda thought!
Human progress isn't measured by industry. It's measured by the value you place on a life.
Just, be kind.