Samuel Martin has an interesting take on what it means that Paul sat at the feet of Gamaliel:
In his first Jerusalem trial (Acts 22:2), Paul introduced himself to the Sanhedrin as he who learned “at the feet of Gamaliel.” This phrase means more than we would take it for at first glance. It sounds like Paul is giving homage to his teacher, and that he hung on Gamaliel’s every word. Actually, Paul used this figure of speech to remind the Sanhedrin just how important a figure Saul of Tarsus was, even from his earliest years in Jerusalem. In the synagogues, students sat in an arrangement that reflected their academic position. We have a description of a typical academic synagogue setting in which Paul would have studied:
“The academy head presided, seated on a chair or on special mats. In the front rows opposite him sat the important scholars, including his colleagues or outstanding pupils, and behind them all the other scholars. When the academies grew larger, particularly in Palestine, the order of the seating was based on a precisely defined hierarchy. In the first row sat the great scholars, in the second row the less important sages, and so on” (Adin Steinsaltz, The Essential Talmud).
We can, therefore, picture the apostle as a young man, seated front and center, at the very feet of the renowned and revered Gamaliel. Already at the top of his class, he was on his way to becoming the leading Pharisee.
Compare it to this text:
Luk 10:39 And she had a sister called Mary, which also sat at Jesus’ feet, and heard his word.
Was Jesus’ star pupil a woman?
Whether or not this was the case, we know that rabbinic students were not expected to only learn, but to teach what they learned to others.