Claremont School, Anne M. Dorner School and Ossining High School were placed on lockout for approximately one hour from 1:30 p.m. to 2:30 p.m.
The district said police were investigating the matter. The school followed normal dismissal procedures and after school activities went on as scheduled.
In a lockout, no one can enter the building but classes continue.
In September, Ossining High School was placed on lockdown after an anonymous threat on social media.
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