NASHVILLE - Gov. Bill Haslam is moving to cap enrollments at Union County's rapidly growing online public school run by the for-profit company, K12 Inc.

First-year K12 Inc. student standardized test results last year were called "unacceptable" by Education Commissioner Kevin Huffman.

An administration bill effectively caps student enrollment at any virtual school to 5,000 students. The school's director last month estimated current enrollment at 3,200 students and projected enrollment would exceed 5,000 in the future.

The bill also implements stricter initial enrollment limits tied to performance for any new online school established in Tennessee. Enrollments would be limited to 1,500.

Enrollment of students living outside the local school district that establishes the virtual school can't amount to more than 25 percent of the district's enrollment.

"However," the bill states, "any public virtual school in operation as January 1, 2013 may continue to serve the students enrolled in the school as of January 1, 2013."

The Haslam administration had no immediate comment. The governor did not mention the bill Monday in his State of the State address to lawmakers.

K12 Inc. operates the online school as the Tennessee Virtual Academy, which was approved by the Tennessee General Assembly after a heavy lobbying effort by the publicly traded company.

The state's figures show the Tennessee Virtual Academy fell into the bottom 11 percent of schools for student gains as measured under the state's Tennessee Value-Added Assessment System. The cyber school scored a 1 on the 5-point scale.