I've seen a Wall Street Journal article claiming there is no verifiable evidence.
I've seen YouTube videos treating it as fact.
In my school days it was treated as fact.
I don't know what to make of the Thomas Jefferson//Sally Hemings thing. Can someone here bring me up to date on the latest evidence sans political influence?
More can always be written, but you may be interested in these two previous answers:
"Is there conclusive answer to the Jefferson - Hemings question? Was it Thomas Jefferson or is their evidence it could have been another jefferson?" by /u/Talleyrayand
"Did Thomas Jefferson have sexual relations with female slaves other than Sally Hemings?" by /u/uncovered-history
The TL;DR version is, there is DNA evidence linking the offspring of Sally Hemings to the Jefferson family. While there has been some argument that the true father is Thomas's younger brother Randolph Jefferson, this is very much a minority view. Thomas Jefferson was Sally Hemings's slaveholder and came in daily contact with her. As Talleyrayand details, there is reason to believe Thomas Jefferson was the only Jefferson present at his Monticello estate in the months when some of her children were conceived. The broader consensus is that the Jefferson who fathered her children was Thomas Jefferson.