|OK, not sure about your question.|
You stated you wanted a dropdown which to me, means a Data Validation list.
You then stated, as an example: IF(StudentClass="Nursery)
which I took to me mean, that there can be other StutdenClass besides Nursery, which equates to a Dependent Data Validation.
Is all you want a simple drop down of all the Nursery Students?
If you have already given the student list a name, IE Nursery
then select the cell where you want to drop down list to appear
and on the ribbon select Data Validation,
In the Data Validation window under Validation Criteria
change it from Any Value to List
In the Sources box, enter your Named Range, IE =Nursery
Is that what your looking for?