"I'm scared. I've always lived in the big city. I'm going to Grinnell in the middle of basically nowhere," Sandra Herrera, a Carson High graduate, acknowledged during one of the meetings. "The only thing that gives me comfort is my posse."
Higher education experts said the posses' built-in support network fills an urgent need for students who might get lost in the competitive shuffle of college life.
"They are making these kids resources for each other. That is a spectacularly well-thought-out approach," said Patrick Callan, president of the National Center for Public Policy and Higher Education in San Jose.
So far, 90% of posse students have finished college within five years, and most finish in four, the Posse Foundation reported.
That contrasts with the 53% of all students nationwide who earn bachelor's degrees within six years, according to the most recent federal statistics. The figures are lowest for minorities: Only 40% of Latinos finish within six years, while just 37% of African Americans make it.
Researchers said the low minority graduation rates were due partly to the isolation these students experience on campuses such as Grinnell with overwhelmingly white enrollments. Seventy-eight percent of Grinnell's 1,400 students are white.
"It's not enough to take a kid and dump him on a campus," said Walter R. Allen, a UCLA professor who studies issues of diversity in higher education. "You have to be in situations where you can succeed. That requires the presence of some like-minded souls. Those who come in without any kind of support or connections are more likely to fail."
While universities in the posse network have touted its benefits, the program hit some early snags. Two universities -- Lehigh in Pennsylvania and Rice in Texas -- dropped out in the early 1990s.
Lehigh took two posses but quit because of communication problems with the foundation, not because of anything to do with the students, a college official said.
Rice also accepted two posses for its engineering program, but one professor said the students were unprepared.
"They had to run too fast, too soon. They weren't doing well academically," recalled Richard Tapia, a mathematics professor in the engineering school. "From the very start, I certainly doubted that just the philosophy of a strong [team] was going to be sufficient for these students to succeed at Rice."
Bial, the Posse Foundation founder, stressed that 16 of the 17 posse students at Rice graduated from the university, most of them in engineering, and one transferred to another college.
She said the foundation, the university and an outside minority engineering organization that helped select the students decided together to discontinue the posses there because of philosophical differences over how to run the program.
Grinnell accepted its first posse of 12 Los Angeles-area students last year. All of them did well and are returning, joining the 10 newcomers in Jimenez's posse, university officials say. The college will have 80 posse students on campus within four years, including others from Washington, D.C., accounting for about 5% of its students.
Grinnell President Russell K. Osgood, who helped pick the first Los Angeles posse, said he was impressed by the students' serious attitudes and supportive approach.
He's not worried about the students' high school grades or SAT scores, pointing out that they will meet as a group weekly with a university mentor during the first two years on campus as a part of the posse program.
"A lot of colleges work hard to admit diverse students, but don't do enough to retain them," Osgood said. "One of our interests is not only getting diverse and interesting students, but [having] a support structure so they will stay here and graduate."
Emerson Molett, part of Grinnell's first Los Angeles posse, is one of those staying.
The Westchester High School graduate said his fellow posse students helped him last year as he struggled to adapt to Grinnell, where professors are demanding and the snow falls steadily from Thanksgiving until spring. He also had to adjust to small-town life in Grinnell, a central Iowa community of 9,105 people, not counting the college.
The African American student said he and his posse mates edited each other's research papers. And he recalled how one-on-one talks with his Grinnell mentor provided an important outlet to vent frustrations.
"Sometimes you just need to talk and know that someone genuinely cares about you," said Molett, 19, who earned a 2.8 grade point average his first year. "I was really homesick first semester," he said. "It really helped to know that someone from L.A. was feeling the same thing."
Jimenez already is feeling many of the same emotions -- and classes haven't even begun.