If you are referring to your SIS Parent Portal account, no, parents cannot delete students from the account. You would need to reach out to the district and work with them to remove a student.
If you are referring to the PowerSchool Enrollment account, parents cannot remove students from the account once added.
Parents have the option to cancel an in-progress application form but they cannot delete an already submitted registration form for the student. You would need to reach out to the district to withdraw the submission.
You can check out the FAQs related to the enrollment process here.