Why is Jeff studying Spanish? He clearly states that he was a lawyer working for a law firm, who is at risk of getting disbarred when they discover he has no degree? How does a Spanish degree qualify you to practice law?
He's not getting a degree in Spanish, he's simply taking the classes required to graduate, which includes 2 credits of a foreign language. So Jeff and the study group took Spanish 101 the first semester of their freshman year, and then Spanish 102 in their second semester. After that they don't take Spanish anymore, because they took all of the Spanish that they had to in order to graduate :)
in the first episode jeff wanted to impress britta and he saw that she was studying spanish so he told her he had a spanish study group in case she needed any help and she said yes so thats where it started.