What do control groups prevent when a city implements a new, expensive after-school tutoring program without one?

Answer

Spending public funds based on promising initial scores that would have occurred anyway due to natural progress.

Without a control school experiencing the natural academic drift, the city cannot confidently determine if the expensive new program actually caused the score change or if it was simply the natural progression of students through the curriculum.

What do control groups prevent when a city implements a new, expensive after-school tutoring program without one?
experimentconclusionresearchmethodologycontrol group