Wisconsin's public school open enrollment period begins Monday, and for the first time, families will have three months to decide whether and where to enroll their students outside of their home school district.

For the Madison School District, the extra time could mean more families choosing to leave for other districts or virtual schools, though Superintendent Dan Nerad said it's too early to know what the affect will be.

"By the nature that there's an open window, that's likely to happen for us as well as other districts around the state," Nerad said.

Gov. Scott Walker signed legislation last week extending the official open enrollment period from three weeks in February to three months. Applications must be completed by April 30.

Proponents of the change, including school choice advocates and the virtual school industry, tout open enrollment as giving parents and students more control of their educational options.

Republicans in particular have embraced open enrollment for unleashing market forces on school districts, which lose nearly $7,000 in state aid for each student who leaves. The money travels with the student to the new district, and some of the biggest gainers are those with online schools.

Others, including Madison district officials, worry the extended window will create administrative problems as they try to set their budgets and project school class sizes for next year. To address that concern, the Legislature also extended the date by which districts must issue teacher non-renewal notices from mid-March to mid-May.

Madison has seen a growing number of students leave through open enrollment in recent years, especially after a 2007 U.S. Supreme Court ruling ended the practice of denying open enrollment transfers based on the racial balance of school districts.

The district had 913 students leave and 213 students enter this school year, a net loss of 700 students. That's up from a net loss of 592 students last year and 82 students five years ago.

A 2009 survey of families opting to leave the district found that more than 60 percent mentioned "environmental issues" related to safety, drugs, alcohol and bullying in the schools. About 42 percent said the resident school was closer to home, work or daycare and 18 percent made reference to the district's limited curricular offerings. About 15 percent said their children transferred to a virtual school.

Nerad said the district has made changes to respond to those concerns, such as improved school security, more talented-and-gifted programming, and the expansion of dual language immersion classrooms.

It's hard to tell if those changes have made a difference. Nerad said the district may conduct another survey and in coming years will explore opening theme-based magnet schools, which could attract more students to the district.

Andrew Statz, the district's chief information officer, noted the number of new families choosing to leave the district may be declining.

This year, 333 students left the district for the first time, up from 318 last year and 263 in 2009-10. But for the first time, this year's number included 64 4-year-old kindergarten students, who couldn't have left in past years because Madison didn't have a 4K program.

"We have to have a conversation about what do open enrollment levels mean," Statz said. "We need to understand the dynamics behind it."