Portland Public Schools today sent a letter to its non-union employees warning them that they are expected to show up to work Feb. 20, even if teachers go on strike.

"You do not have a right to strike," writes the school district's chief human resources office. "This does mean that you may need to cross a picket line of teachers."

Classified staff who are not teachers include secretaries, clerks, cafeteria staff, custodians, occupational therapists and physical therapists.

The Portland Teachers Association voted a week ago to authorize a walkout starting Feb. 20. While the school district and union continue to negotiate, Portland Public Schools has begun hiring replacement teachers on Craigslist.

Here's the full letter to school employees, sent at 2:52 this afternoon.

Dear Valued Non-Represented Employee, The Portland Association of Teachers (PAT) has notified the District that they will conduct a teacher’s strike starting on February 20, 2014. The District’s highest priority is keeping schools open to continue to support students and families by providing a safe and secure environment. This letter is to notify you of the District’s expectations during a strike by PAT.  Because we intend to remain open and serve students during a strike, there will be work for you to do that is within your job classification.  You do not have a right to strike. This does mean that you may need to cross a picket line of teachers.  Please be assured that the District will make every effort to ensure a safe and secure working environment for all employees and students. We expect to have some visible way to designate staff who are required to work.  At this time, our emergency service continuation plan calls for schools to be closed to students on February 20, 21, and 24; however, these will be required work days for all other employees.  We will be asking some of our non-represented employees to assist in keeping schools open to continue to support students and families by providing a safe and secure environment. We plan to prioritize opening elementary, middle and PK/K-8 schools, with high schools to follow.  This means that you could be assigned to a school and/or different hours to assist with this effort. Your supervisor will be talking to you if you are needed. We hope to notify staff by Monday, February 17 if you are needed to work at schools.  Training will be provided on February 20, 21 and 24.  If you are asked to assist you will receive specific details of where and when the training will occur and what your assignment will be. If you are less than full-time, we may need you to work more hours. Please complete the attached form indicating your availability to work additional hours. You will be contacted if we need you to work additional hours, and you will be paid for this additional work consistent with existing pay provisions. Additional information will be shared with you as soon as possible. Please be assured that the District is making every effort to reach a contract settlement without a strike.  The District appreciates your contributions to the students and thanks you in advance for your continued professionalism during these challenging times.  Sincerely,Sean L. MurrayChief Human Resources Officer