A lot of people seem to be getting confused about the hourly rates and job description details. There are so many variables.
It is not enough to say, "well you work a part time role, you get paid less". It's the hourly rate that's really being discussed. Of course you take on the role knowing you're only ever going to get paid for part of the year. I don't think anyone here is asking to get paid the FTE for no extra work (although, when I first started that was the done thing in one of the LAs I worked for. Interestingly enough, the LA across the border did not. How is that fair??).
At the end of the day, I feel like what is needed is a nationalised payscale for TAs (I'm sure a lot of people mistakenly think it's a UK wide payscale like teachers).
The grades/job descriptions should be clearly reflected in the paygrades and these need to be nationwide too. Yes certain parts of the job can be done with no qualifications however there are certainly some expectations in certain roles (like a few people have said - teaching whole classes and planning work for example) that absolutely cannot if you don't want to end up with carnage (which I've witnessed this a few times). We should not be looking at people getting paid at the bottom end of the scale and taking on these huge responsibilities because "thats what the job entails"! The roles should be recruited for and the grade paid accordingly and relevant tasks given to the correct level employee instead of getting someone in at grade 1 and expecting them to do everything (job descriptions in this sector often list a bunch of stuff and then bung on "and any other task relevant to the role" or similar so are ultimately meaningless. I realise a lot of schools will be doing this because they don't have the budget for anything else.
Just as an aside, it really grates on me when you read threads on here about people working from home on huge salaries, worried that they don't actually do much to earn their money and then others reassuring them that it's ok because the more experienced you are, the less you have to work. People get paid more for experience apparently. It's certainly not the case in this role!
Over qualified people might choose a TA role because it suits their childcare and mental health needs. They are prepared to take a pay cut. I don't see why that means they can't state that they feel they're being taken advantage of. They're there because they find the work meaningful and are not asking to keep their teacher's wage and simply do less. They're just asking for pay to be reflective of their daily work.