Police are searching for a 15-year-old student with special needs who left her Brooklyn school Monday and has been missing since, authorities said.

Nashaly Perez began attending special-education school PS 371 full-time this September, her mother, Sandra Rodriguez, said at a news conference Wednesday.

Nashaly suffers from mental and emotional conditions including bipolar disorder and ADHD and takes medication to stabilize her mood and treat hallucinations and suicidal thoughts, Ms. Rodriguez said. An individual education plan, required for all special-education students, for Nashaly states she should have an aide with her at all times on school grounds, Ms. Rodriguez, 32 said.

Ms. Rodriguez said she went to pick up Nashaly from school early on Monday. She said her daughter's aide was outside the school when she arrived and told her Nashaly was missing. Ms. Rodriguez said she went to see the principal, Joan Antonelli, and was the first person to call police.

Education-department officials said Ms. Antonelli has been reassigned to an administrative post pending an investigation, and that she doesn't have a disciplinary record. The Council of School Supervisors & Administrators, the union representing principals, declined to comment, saying, "Right now the concern is for the safe return of the child."