In the Democratic primary, Valarie Wilson and Alisha Morgan were leading in unofficial returns with at least 86 percent of precincts reporting.
On the Republican side, Michael Buck and Richard Woods were in the lead.
Primaries in both parties seem almost certain to head to a runoff as state rules require a candidate to receive 50 percent plus one vote to advance to the general election.
The seat is being vacated after a single term by Superintendent John Barge, who was one of two unsuccessful Republican primary challengers to Gov. Nathan Deal.
On the issues, Democrats seemed to agree on the need for more spending on public education and their support of the multistate Common Core school standards.
They split on the subject of school choice, with five of the candidates attacking Morgan for working with Republicans in the General Assembly on bills that offered parents taxpayer-funded options.
When the Republicans talked about issues, they divided sharply over Common Core. Three of them – Allen Fort, Mike Buck and Kira Willis – endorsed each other in an Atlanta Press Club debate Sunday, because they agree with keeping Common Core and argued their experience as career educators made them best suited.
None of the candidates raised enough money to go on television or mount much of a statewide campaign. As a result, voters relied on personal contacts, friends and endorsements.
Morris News Service’s Walter Jones contributed to this report.