Translation:Her children are going to three schools.
I think you were joking, but just in case you didn't understand, there are families who have, e.g., one child in elementary school one in a middle school & one in a high school.
Is "different schoolsl for each kid implied or would it normally be used? Three schools is a thing, if you go to votec (vocational training) or charter school (for science or architecture, etc.) out of your district, they'll bus you to the other school for the morning and then bring you back to your regular school in the afternoon. If you go to Hebrew school or whatnot, etc. That's three schools. Your kids could be in different programs and all get bussed, so all go to the same three schools.