Newport-Mesa Unified School District trustees announced their decision Wednesday after a meeting, the Los Angeles Times reported.
"As a Board of Education, we are unanimous in our resolve to ensure the academic integrity ... as well as in delivering justice for the cases before us," said board President Karen Yelsey.
Newport police began investigating the alleged cheating plot in June when a Corona del Mar teacher notified administrators someone may have accessed her computer and altered grades.
By December, 12 student had been identified as suspects, along with private tutor Timothy Lance Lai.
Police searched Lai's home, but he had left and has yet to be located.
Police said Lai allegedly instructed students to attach a keylogger -- a device that can monitor keystrokes -- to several teachers' computers. The students then allegedly hacked into the district computer system, changed grades and accessed English, science and history exams.
The 11 students who were expelled and Lai may face criminal charges. The search warrant for Lai's home indicated police were investigating possible felony counts, the Times said.
The school district is now examining the records of 52,000 students to see if any other grades were changed this year.