ScholarPack does not store historic Form group data, so any movement of students between forms will be live and affect registers.
Also, any change will mean you cannot run attendance reports based on the previous form group.
If any new form names are required, these can be set up in advance at Admin>Config>Core Setup>Forms.
After the close of registers on the last day of term prior to the change, students can then be moved to their new form groups via Admin>Students>Group Updater.
Select the student year group and use the Student Attribute 'Current Form Group'.