The Broward County School District said the calls, handled by service provider ParentLink, accidentally went out between 10 p.m. Monday and 4:40 a.m. Tuesday.
The calls advertised next month's re-engagement fair for dropouts, the South Florida Sun Sentinel reported Wednesday.
"It was a good message, just bad timing," said Tracy Clark, public information officer for the district. "It was not intended to be intrusive or an inconvenience."
ParentLink said an accidental override in the system caused the late night calls.
"As far as I know, this is an extremely rare situation," ParentLink marketing director Adam Bushman said.
The school district and ParentLink released a joint statement Tuesday apologizing for the calls.