In his essay in the Des Moines Regiser, T.J. Foley made at least two errors in the conclusions he drew from the statistics he used in his essay opposing changes in collective bargaining as it applies to teachers. (See link below.)
First, assuming it is true that test scores are higher in schools with unionized teachers, he provided no evidence that the existence of unions is the cause of higher test scores. It very well may be that unions are more often present in larger cities with higher incomes and larger schools, and that the higher scores are caused by those factors rather than the fact that a union is present.
Second, assuming it is true that the average teacher in Iowa earns 7% less than median household income in Iowa, that statistic is meaningless. Teachers are individuals and many households have more than one earner. Comparing individuals to households is simply not valid.
It is very difficult to say whether it would be better or worse for students if teachers lose some of their collective bargaining power. T.J. Foley’s essay did not clarify that issue.