For new TAs – or experienced pros who are still getting their feet wet with Unity – there are a couple of new Unity-sponsored courses that can hep you learn basic Unity concepts and techniques
Unity Essentials is an introduction to the Unity ecosystem:
https://learn.unity.com/pathway/unity-essentials
and Junior Programmer is oriented towards preparing you for Unity certification, which can be a useful credential for a first job.
https://learn.unity.com/pathway/junior-programmer
There’s some more background here