The attack happened New Year's Eve morning in the north-central town of Danskin as children were tobogganing on a hill outside the schoolhouse, the Vancouver Sun reported.
Mary Metzler, mother of two of the children, was cleaning inside the school and ran to see the large cat on top her 7-year-old son, the report said.
She said she didn't stop to look for a weapon and used a wash rag to lash out at the cougar, which backed off, the Sun said.
The boy required 22 stitches for his wounds and was expected to make a full recovery, doctors said.
The first cougar attack happened Saturday in the town of Boston Bar when an 11-year-old boy stacking firewood was saved by his retriever dog, Angel, who blocked the cat's lunge. A Royal Canadian Mounted Police officer who happened to be nearby shot and killed the cougar and the dog was treated for injuries and was to be released from veterinary care Tuesday, the Sun said.