After a second stint as New Jersey education commissioner, David C. Hespe is stepping down.
Hespe announced Friday that he would resign effective at the end of September. He was named by Gov. Christie in February 2014.
His timing coincides with the beginning of a new school year for more than one million New Jersey public school students.
"We are entering another school year, which represents a time of transition for thousands of students. Just as they will be embarking on a new stage of life, I have decided that the time is right for me to do the same," Hespe said in a statement.
Christie named Kimberley Harrington, the department's assistant commissioner and chief academic officer, as acting education commissioner.
In a statement, Christie credited Hespe with overseeing sweeping changes in education, easing regulations for districts, and expanding the use of technology in the classroom.
"For over two years, David Hespe has been working for the betterment of New Jersey's students, educators, and schools," the governor said. "Unquestionably, New Jersey's students are more college- and career-ready and in better position to succeed thanks to the tireless efforts of Education Commissioner David Hespe."
Hespe plans to explore new career opportunities in teaching and learning, the statement said. Hespe, a lawyer, has served multiple roles in state government, as well as K-through-12 and higher education.
He served his first stint as education commissioner under Republican Gov. Christie Whitman from March 1999 to March 2001.
Ten years later, he joined the Christie administration as chief of staff for former Education Commissioner Christopher Cerf, serving from August 2011 to September 2012.
He also was president of Burlington County College (now Rowan College at Burlington County) from September 2012 to February 2014, when he resigned to become commissioner again.
During Hespe's most recent tenure, the state switched to a controversial new standardized test for English and math in 2015 - PARCC (Partnership for the Assessment of Readiness for College and Careers).
Amid a heated debate about the test in the first year, parents kept scores of students out of the testing. Some teachers and administrators were concerned about how the results would be used to evaluate their schools' performance.
The test, aligned with the equally controversial Common Core educational standards, is given to students in grades three through 11. Teacher evaluations are tied to test performance.
Opponents argued that schools were given insufficient resources to prepare students, that the test limits instructional time, and that it will have consequences for students who do not perform well.
The first results, released last October, found that New Jersey students, especially high schoolers, were lagging tremendously in math. About 44 percent of the state's 11th graders were college-ready, according to the results.
Hespe has defended the test with an appeal for "social justice" for New Jersey's children. More rigorous standards were needed because too many students were graduating unprepared, he said.
In his statement Friday, the commissioner acknowledged that the department "implemented a number of very difficult but extremely impactful initiatives." The state also added more charter and "Renaissance" schools in Camden and other urban districts.
Harrington, a former classroom teacher, has more than 20 years of experience in education.