The teacher will be helping every table, ensuring work is being done. Honestly KS1 is just frenetic, children don't stop moving, rocking in their chairs, tapping table legs, balancing pencils on their lips, distracted by things going on because they are just 6, they are not soldiers all sitting perfectly still. It is expected that they try to sit still and get on with their work.
I used to volunteer in a primary school, I have a degree and I took some relevant education courses including SEND to enable me to understand and help more. This very long post is just to give you a look inside a classroom.
Originally the school did sets, so 90 year intake, 1 class high ability, 1 class middle ability and one class low ability that had all 3 TAs plus me in the classroom. Everyone moved classrooms for English and maths. This then changed and everyone stayed in their classrooms and they went to mixed ability tables. Yes it does benefit the low ability students because there is peer on peer teaching too which cements the concepts for the higher ability children too but this is KS2 not KS1.
Depending on the amount of space in one classroom I had my own table and low ability children came to me and I oversaw about 4 or 5 children. Mainly making sure that they are engaging with the work, being their cheerleader and making them realise that they can do the work. It isn't beyond them and teaching them resiliance. This is far easier than me trying to get to every table with a low ability child on. I can see instantly when a child isn't writing if they are sat with me. Some children know they can just run the clock out on the lesson before break and it does them no favours in the long run. Higher ability children are given "differentiated work" to push them as they complete the work relatively quickly.
For behavioural issue children they used to be taken out of the classroom and given 1 on1 or 1 on 2 to help them get through their work. Sometimes because of the behavioural issues and not engaging with work they fall behind, ie I had year 5 children working at a year 2 level. We cannot accommodate that teaching in the classroom. It is difficult to try to keep their attention when the class is doing something entirely different. Also as a volunteer I am not trained in dealing with violent children who break the fingers of staff, slam books into their faces, kick and spit, oh and the lickers, who know that licking someone's face/hand/arm is awful and do it anyway to staff etc so the classrooms I am put in do not compromise my safety. By the way this is an outstanding school in a lovely area and this was pre covid.
Lack of funding now means there are less TA/LSAs and so that extra help in the classrooms is disappearing. It was at least 1 TA per class, I can see from their staffing that that is no longer the case. Some of those TAs will disappear from the classroom to become cover supervisors ie teach a class in the afternoons when no core subjects are taught. Teaching staff have PPA time which means they are not in a classroom. Their class is covered by a TA, so art, PE, tech, assembly, hymn practise etc.