If appropriate for your school, you may still record this information on the student profile, on their extended tab under the Personal Information header. This sits just below where you would record the student's First Language.
If you need to apply PIE to a large number of students, you can do this in Group Updater (Admin > Students > Group Updater), and select Proficiency in English from the Student Attribute drop-down:
You can report on PIE via Reporting > Reports > Students (tab) > Languages/EAL.
If you wish to remove all records of PIE in ScholarPack, due to no longer needing this data for Census purposes, you can go to Admin > Students >Bulk Data Deletion.
Here you will find three areas the DfE no longer requires data collection for (PIE, Nationality and Country of Birth).
You can click Check All, to select all students, and then remove the data in bulk at the base of the student table by selecting Remove PIE.