Since only one of those children was of school age, I am not sure that she was schooling "all the children." It was a horrible situation, but I don't see what homeschooling has to do with it. Maybe the oldest one could have spared if he had gone to school, but there's nothing to keep a crazy person from waiting until school is over for the day before murdering.
The whole lot of them should either have been in daycare or in a relative’s care (obviously better if available) during all hours that their father wasn’t home. Leaving young children at home with a patently insane mother makes no more sense than hiring a nanny who you know to be currently suffering from full-blown insanity and leaving the kids with her all day while both parents go off to work. Crazy people are not able to care for young children.
Some people don’t understand that many insane peopel are skilled at planning things out and being deceptive. Andrea was planning on killing her kids, that’s why she locked the house up so the kids wouldn’t get away.
This woman is the same. She didn’t have empathy or natural love for her child. Some people are plain evil.