Superintendent Robert Schiller requested the leave of absence, which runs until Sept. 30.
The new Illinois Board of Education that was appointed by Gov. Rod Blagojevich named Randy Dunn as the interim state superintendent.
Brenda Holmes, a newly appointed member of the board, says Schiller "absolutely" will be replaced.
She says the governor's office recommended Dunn for the interim job, but she doesn't know whether Dunn is likely to become the permanent superintendent.
Schiller has nearly a year left on his contract with the board. Board members authorized negotiating a deal for him to set aside with a maximum payment of $160,000.