An issue has been reported that the "Hide Current Info from Students and Parents when Teachers are Updating Grades" portal option is not being honored in the parent/student portal, allowing parent/students to view the grade mark currently being edited by teachers.
If Grades needs to be hidden from parents and students, an immediate workaround is to deny Read access to Grades under Portal Groups security for both Parents and Students. This will hide the Grades page completely.
This issue has been reported to programming, and a fix is currently underway. This issue has been occurring since the 9/1 version of Aeries.
This issue was fixed in the 9/26/2017 update:
Fixed: Grades: This page was not honoring the "Hide Current Info from Students and Parents when Teachers are Updating Grades" option, fixed.