As the supervising teacher, school principal or area superintendent, you may be required supervise, monitor or write an assessment about a teaching assistant. To do that right, you have to observe her in the classroom, in the school and on the playground. Informal observation happens automatically whenever you meet the teaching assistant in the hall or in the staff room, and these interactions will help you create an impression of the person that will factor into formal assessments. Formal observation requires more planning, as it is generally used as the basis of an assessment or teaching appraisal.
Schedule a time to observe the teaching assistant. Let him know in advance when that will be. If you are the classroom teacher, you can say something like, "Tomorrow morning from 11:30 to 12, I'm going to sit in the back of the classroom and watch how you work with the students as they will be doing their math at that time."
Make a list of skills and attitudes you are going to look for based on the teaching assistant's job description. This might include things such as preparation, interaction with students and presentation skills.
Observe the teaching assistant and try to be as unobtrusive as possible. Take notes as you are watching her, because it will refresh your memory when it comes times to write your report.
Work from the form you designed or one that is provided by the school administration. A 1 to 5 scale is the best way to rate performance of teaching staff in each category.
Write your report --- if it is required at the end of the form --- as soon as possible after observing the teaching assistant. The longer you leave it, the more difficult it will be to recall details.
Have a debriefing session with the teaching assistant. Provide positive reinforcement and suggest areas that could be improved. Leave him with a copy of your observation report.
Schedule a follow-up observation appointment. Mark it in your diary and have the teaching assistant do the same.