Thank you for reaching out to the PowerSchool Community for assistance!
To provide better assistance, would you please share the name of the PowerSchool product in which you have accidentally deleted the assignment? Example - PowerSchool Student Information Systems, Unified Classroom, etc.
Currently, there is not any feature to undo a deletion or revert/retrieve a deleted assignment in Unified Classroom. The best we can do is set up a Test Server with a data pump from before the teacher deleted the assignment then allow the teacher while using the data from the Test Server to recreate the assignment in their live side Gradebook in Unified Classroom.
If you would like to explore this process, I recommend reaching out to the Designated Support Contacts within the district who should be able to create a case on your behalf and provide the support team the Date and Time to request a Test Server to be established.
Meanwhile, you can submit an enhancement request directly with the Product team for this feature through the PowerSchool Ideas Portal. After submitting your idea on the portal you can track the status. You can also view the existing ideas on the Ideas Portal and vote on them.
To learn more about the Ideas Portal, we recommend reviewing the article on PowerSchool Ideas Portal FAQs