I'm a teacher so can't advise from personal experience of the role, but as long as you're prepared for the appalling pay, it will give you great experience being in the classroom every day and learning from the teachers around you. Many teachers do start off this way.
Each year group is different. I'm in Reception so a big part of my TA's role is assisting me with setting up the environment, helping to create engaging role plays and small world set ups etc. I generally come up with the initial ideas, based around our learning, but I'm more than happy to take on my TA's suggestions. They also assist during carpet inputs (usually sitting with children who need support to focus). Throughout the day they listen to readers, run small intervention groups and support the children in provision. In Reception, there's often at least one child in nappies each year, unfortunately, who our amazing TA's usually take the lead in supporting.
Other year groups will be different, in that you'll probably work with groups each morning to support in English and Maths, but it's pretty common for most TAs to listen to readers and run intervention groups in the afternoon in Primary, whatever the year group.
Whatever the age group, you'll be expected to show initiative with behaviour management. The teacher is ultimately responsible for dealing with major misdemeanors but, if you're lucky, your teacher will hopefully view you as an equal in terms of dealing with low level behaviour and let you deal with incidents as and when they occur, if you're first on the scene. This will be great experience for you.
I'm sure you'll find it a very worthwhile experience. If your school are aware of your plans to go on and train to be a teacher, many will support you with this and give you extra responsibilities, should you want them, to help prepare. They may even offer you the opportunity to train with them as part of the SCITT program, if they offer this at their school, which many prefer to the PGCE route.