Students(tab) - > Select the number of students you want(Ctrl+A for all of them) -> Edit -> Transfers -> Copy to another Period.

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After that , a screen will pop-up where you should again choose what kind of customization you want concerning the students.
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After pressing "Continue" , a grid in which you see all the students(and some data about them) you want to transfer and some options you may want to configure.
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Pressing "Save" will start the transfer.