Superintendent Craig Carr told Newsday he had not yet received the letter and declined to comment.
Hundreds of students at Ralph G. Reed Middle School walked out of school on April 1 to demonstrate in front of the district’s administration offices.
The NYCLU said it hoped the district would expunge the suspension from the students’ records.
It said the suspension sent a message that free speech is unimportant.
(TM and Copyright 2011 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2011 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)