I need to obtain public school video that former attorney failed to obtain. I need this video footage for any further action that may be rendered toward me in the future.
In Texas, am I allowed to subpoena these videos without a cause number?

Do you have a case before the court? If so, then there is an index number.

well ... rather then seek opinions how to approach the subpoena try researching the jurisdictional law such as local rules of procedure, state rules, federal rules...statutes that control subpoena and case law in the trial court and the court above the trial court.

this course shows you how to get at what you are looking for.

yes it's a lot of reading.