What was one practical benefit of common lessons in old education?

Correct answer: Children could discuss with each other

The correct answer is A. Common lessons brought children into the same learning situation, so they could ask questions, exchange ideas and help one another understand difficult material. This is a practical advantage of group learning, not merely an emotional benefit. Discussion allows a learner to hear another explanation, correct an error and develop communication skills. The story contrasts this possibility with Margie's solitary machine lessons, where the teaching device provides information and testing but no classmates for direct interaction. Options B and C are unrelated inventions, while D is incorrect because old schools did have teachers; the point was that teachers worked with groups in a shared setting. Thus the concept is collaborative learning through peer interaction.