You are preparing a return for two taxpayers but focused on only one.  The expenses were also incurred by the husband -- it's an interesting point, that he might not have been teaching school during some of the time the wife was at home, but teachers don't typically sit around doing nothing and avoiding work that is employment related during the summer, even if they are not in a classroom.  There is nothing in Section 21 requiring both spouses to be employed at the same time.   For one thing, that would require step-parents to provide care for stepchildren.