When the question (what qualifications do you have?) has been asked on the TES TA forum in the past it has been found that quite a few TAs have a degree or a 'higher' qualification in the area of work they pursued BC (before children). Many find TAing a stimulating job which has very convenient hours for a mum with young children, so long as you don't mind the poor wages.
I think the problem of poorly (or un)qualified TAs arises because some HTs seem to regard the job more in in the light of paid volunteering rather than a para-professional type of job. So that nice mum who comes in to listen to the children read gets offered the job when a TA post comes vacant. With absolutely no consideration of qualifications. I also wonder if this is because some HTs do believe that TAs are really just another handy body around the place?
Then, of course, the 'nice mum' TA is handed all the so called 'low ability' & SEN children to support and to withdraw for interventions in Literacy & Numeracy. A practice I have always thought to be very odd.
However, this sometimes works when an intelligent and interested TA makes it her business (because they are nearly all women) to research and learn about the most effective ways to help the children she works with. Some TAs may develop more expertise than teachers in a particular area.
Our LA is trying very hard to ensure that all TAs are qualified in some child related subject to at least Level 2. I don't think that the L2 Maths & English are a requirement, though. Which is a worry because those are the two areas where TAs are most likely to be used in support.
in the secondary I work in we always require a C or above in GCSE Maths & English.