I am a TA in a primary school. One of the teachers has me to cover the class for an hour or so, about once per fortnight while she and the rest of SMT have a meeting (during numeracy in the morning).
She will not do without a TA in the mornings generally as she says it's too much to cope with by herself.
Yet when I cover the class, I do it with no TA and I'm not a teacher 
She gives me the planning about one minute before she goes to the meeting. A few times she has criticised me when she came back and the children hadn't all completed the work perfectly (there are a few SEN children as you'd expect and they often don't understand tasks without a lot of support - which is why she needs a TA in there usually.)
Does this sound reasonable that:
- I cover the class at all?
- I am expected to produce the same results as a teacher would?