I made dough for hafrashas challah with my students, and each girl got a piece of dough to bake at home. I forgot to separate challah. What’s the halacha

Dough that is made with the intention of giving out small portions so that each girl will bake it at home does not require hafrashas challah. But if the teacher keeps a large enough amount of dough for herself so as to require hafrasha challah, and gives the surplus to the students, she should do hafrashas challah with a bracha and have in mind to exempt the pieces of dough taken home by the students.

(For more information, see Mishpetei Aretz, §Challah, 2:20)