When Atticus went to Montgomery "to read law," what tradition was broken according to the narrative of To Kill a Mockingbird?

Atticus's study of law in Montgomery broke the long Finch tradition of men staying on the land to farm cotton. The family's ancestor, Simon, a fur-trapping apothecary from Cornwall, had originally come to Alabama by way of Philadelphia, Jamaica, and Mobile. He bought a plot of land on the Alabama River forty miles from Saint Stephens, and, having forgotten what Scout refers to as "his teacher's dictums on the possession of human chattels," he purchases...

Atticus's study of law in Montgomery broke the long Finch tradition of men staying on the land to farm cotton. The family's ancestor, Simon, a fur-trapping apothecary from Cornwall, had originally come to Alabama by way of Philadelphia, Jamaica, and Mobile. He bought a plot of land on the Alabama River forty miles from Saint Stephens, and, having forgotten what Scout refers to as "his teacher's dictums on the possession of human chattels," he purchases three slaves. This phrase is a reference to John Wesley's opposition to slavery. Wesley was the founder of Methodism and a fervent opponent of slavery, but although Simon Finch was a Methodist, he purchased slaves.

After the Civil War, the Finches lost most of their wealth, including their slaves, but retained their land. The family lived on the land well into the 20th century, when Atticus went to Montgomery to study law and his brother, Jack, studied medicine in Boston. Their sister, Alexandra, stayed at Finch's Landing and was married. Atticus and Jack break with the family tradition of living as cotton farmers, and they have other experiences that make them different from most of the people in the area.