Single-sex classes growing at MN middle school

Must be the new school year, because we seem to be reading more and more stories about public schools experimenting with single-sex classrooms.
In Minnesota, Battle Creek Middle School experiments with single-sex classrooms began over five years ago with the number of single-sex options growing to the point where, this year, most of students' classroom time is segregated by gender. Previous incarnations of single-sex classrooms had students segregated for half the day and mixed the other half; but teachers reported an increase in disciplinary issues and lack of attention due to the desire of the students to socialize and have "party time" when they were reintegrated.
This situation--as well as the one in Indianapolis that I wrote about the other day is curious--is there much less socializing among just girls or just boys? Why is it only "party time" when boys and girls are present?
The article is fairly responsible in its coverage noting that no research to date has confirmed the value of single-sex education. It also notes the problem of perpetuating stereotypes, but then, unfortunately, includes line like this based on information from sources:
Teachers said they notice gender differences and tweak lessons accordingly. For example, boys tend to be more competitive and crave physical activity, they said, while girls are more organized.
Makes one worry about what teachers have learned about the research and what exactly they are doing with these so-called well-organized girls and competitive and physically active boys.
Also, no information on whether there are mixed gender options. Lack of such options could be a problem.