Research from the National Institute of Mental Health (NIMH) found that the parts of the brain that command judgment, self-control, emotion and organization are still developing in adolescents, rendering them more susceptible to making poor choices and behaving in emotional or reckless ways. University and college campuses present teens with freedoms they may not be neurologically ready for; an extra year in a more regulated high school program gives them the chance to socially mature further.
A five-year program gives students more time to consider their post-secondary options. In a four-year system, students are under considerable pressure by grade 11 to decide what college/university programs they want to apply to in grade 12 or if they want to apply at all. They may not know at age 16 what field(s) they want to pursue but feel forced to make choices to take prerequisite courses. A 13th grade means that students have the time to take more elective courses, which could lead them to make more informed choices about their post-secondary destinations. Students with more room in their schedules due to the additional year can develop other interests and thus gain opportunities to be more well-rounded. They can participate in a larger variety of extracurricular activities and spend more time building social relationships.
Content-heavy subjects like mathematics are difficult to fit into four years of high school, possibly leaving students less prepared for university-level courses. Countries like the U.K. offer a 13-year system, which culminates in the A-levels, or "Advanced Level" -- two years of study that precede entrance to a university. Schools or colleges that offer this 13th year of education allow students to choose to specialize in areas of academic interest, which offers more time to prepare for the challenges of university-level study.
Five-year high school programs can offer students the opportunity to take advanced placement courses for which they can get credit at a university or college. This helps to offset the always increasing costs of post-secondary education and reduce the time it takes to earn a degree. These kind of courses also allow students to tackle university or college-level content within the supportive context of smaller, high-school-size classes with a teacher they know well.
For example, the Jobs for the Future "Early College High School Initiative," funded by the Gates Foundation, coordinates over 250 schools in the United States where students can graduate with an associate degree or two years of college credit. These types of programs increase graduation rates and, according to the American Institutes for Research findings, support at-risk, marginalized students who tend to do better in learning environments that offer an authentic college link.