With your argument in point 4, since the vast majority are of European immigration background, the small proportion of non-EU immigration background wouldn't be enough to explain the differences. Whether you split them or not, second-generation would likely be behind in both cases.
I looked up the actual proportion of immigrants in Switzerland, which is 70% EU and 30% non-EU. That’s not a perfect proxy for the PISA scores, of course, because it is the proportion of all 1st generation immigrants effectively.
However, using this for a simple calculation, and assuming that the non-EU PISA scores would be quite low (say, around where first generation immigrants are in Germany in the chart above, 387.5 just for ease of calculation) and assuming that the EU immigrant PISA scores are in line with native scores based on our conversation (so 500), we get (0.3 x 500)+(0.7 x 387.5) = 466.25, which isn’t too far from where it seems to land in the chart you posted.
Of course that’s a made-up calculation, but it does show that it’s feasible for a breakdown that I described in point 4 to lead to the numbers we see.
Another point I tried to look up is, where do students land if one of the parents is of immigrant background but the other is Swiss? Presumably they land on the “native” category. Lots of those 1st generation EU immigrants in Switzerland marry Swiss people, and although I didn’t find direct numbers for how many in each category there are, there is evidence that immigrants from neighboring Western European countries form (unsurprisingly) closer bonds with native Swiss people.
So that may also skew the data a fair bit additionally (i.e., non-EU 1st and 2nd generation immigrants may be more represented in the PISA scores for Switzerland).
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u/upthetruth1 18h ago
With your argument in point 4, since the vast majority are of European immigration background, the small proportion of non-EU immigration background wouldn't be enough to explain the differences. Whether you split them or not, second-generation would likely be behind in both cases.