Boucha Bagout, a 35-year-old secretary, and her brother, Dyade, a 29-year-old restaurant
employee, sent the three-year-old to nursery school in the southern French town of Sorgues in September 2012.
They were charged them with "apology for a crime" but in April a court in nearby Avignon found them not guilty.
Public prosecutors appealed against the decision and an appeal court in Nimes on Friday reversed the verdict, passing a more severe sentence than the simple fine that the prosecution had called for.
Defence lawyer Gaële Guenom described the court's decision as "severe, surprising and astonishing", hinting that she might take the case to France's Supreme Court.