Several, but as a % not that many, I think. I'll check. I don't follow incredibly closely as it doesn't affect me personally and I don't have many friends here with children - my close friend lives in eastern France where the first hotspot was, so her young kids' school hasn't opened at all yet. I don't know in reality how many schools have opened and to what extent.
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Looked it up - 70 schools out of 40k primaries that reopened have since re-closed. I can't see yet how many primary schools there are normally.
ETA 50k, so only 80% of primaries have reopened at all.
In my region, they say about 40% of students have gone back for the 1st two years of "college" (secondary), and between 30% and 80% (!) of primary children.