Officials say of the 13, four will be charged with a felony count of Scheming to Defraud for actually taking the test while posing as someone else.
The others are believed to have paid the test-takers to take the test on their behalf.
These 13 are in addition to the seven who were arrested and arraigned two months ago, after the scandal first surfaced.
Those to be charged tomorrow are current or former students of Great Neck South HS, Roslyn HS, St Mary's HS in Manhasset and North Shore Hebrew Academy in Great Neck.
The alleged schemes are not directly related to the original cheating ring, based out of Great Neck North HS, and are parallel cheating rings that are believed to have operated independently.