There are multiple ways to view the relationship between the instructor and the Teaching Assistant (TA). One is to view the TA as a ‘do this’ type of helper; someone to simply help with predefined labs, tutorials, working with students, and marking. This is what most instructors seem to do with TAs. Another way to view this relationship is to leverage the added-value a TA can bring to the equation and what added-value the TA can obtain. This seems to be rarely done. There are other views as well, but we are interested in this added-value model: essentially realizing the potential of the relationship.
An undergraduate TA will bring a different set of opportunities compared to a graduate student TA, but the concept is the same. What experiences, knowledge and perspective does the student bring to the equation and how can this help improve the course? The TA can become an active component of the course design and delivery and contribute to the continuous improvement. The undergraduate TA will have less experience and academic knowledge but will be closer to the students taking the course. They should have the ability to understand the students' expectations and anticipate their reactions. The graduate student will hopefully have more maturity, and ability to work independently, but will still be closer to the student mindset than the instructor is. The TAs can take the first stab at rubrics and even assessments. The TAs can help design, in whole or in part, the tutorials and labs.
As a professional, the instructor has an implicit responsibility to help develop junior members in their field; such as helping the TAs understand the choice of teaching methods, the subtleties of the methods, strengths and weaknesses, assumptions, choice of assessment methods, and the specific details of the assessments. The instructor can share insights about how to review and adjust course delivery. The instructor can help the TAs become self-aware of nuances others take for granted.
These added-value activities require the instructor to be open about feedback made by the TAs, be willing to spend time with the TAs on the tasks, have a degree of trust, and have back-up plans in case things go south. Not all TAs are good and not all TAs will be interested in learning anything from the TA experience. For some, it will be strictly about doing the least amount of work possible for the TA funding provided. Unfortunately, you might have to write them off and give up on them; using them for the simple "do this" tasks.
The added-value approach at first glance looks as if the instructor does not save as much time compared to the ‘do this’ model. The instructor does have to think more and spend a bit more time with the TAs. However, major gains can come from indirect benefits; a better course and a better experience for the students. By engaging the TAs as collaborators and active participants, it is highly likely that new ideas will be developed for the course and these are invaluable. The instructor can become blind to what is happening and what could happen in the course and a great TA situation can help the instructor to see what is actually happening and new possibilities. This of course assumes that the instructor has a growth mindset and does not have a closed mind.