This article explains how to close and reopen assessments in PhD Science Texas.
Close Assessments
When you want to stop accepting student submissions, and the due date of the assessment has not yet passed, you can manually close the assessment.
1. Select Assign from the main menu on the top navigation bar.
2. From the Assignment Library, click the kebab icon next to the assessment you wish to close, and select Close from the drop-down menu. 
3. Click the Yes, Close button to confirm you want to close the assessment.
Reopen Assessments
Teachers can reopen assessments that have been closed or whose due date has passed. Reopening an assessment allows students to update their responses and re-submit the assessment. Students' original answers will be retained, and reports in Analyze will update to reflect the most recent submission.
Assessments must be closed before teachers will see the option to reopen an assessment.
1. From Assign, open the kebab menu and select Reopen on any attempt to reopen the assessment for the entire class.
Alternatively, you can select Reopen from a specific student's score sheet to reopen the assessment for that student only.
Select a new due date from the calendar and click Reopen.