Not usually in upper primary, mixed ability tables are just better, more ideas, more peer on peer teaching, better self worth for all children etc. I am the volunteer (with qualifications) who sometimes has a table in the classroom where children who need extra help come to, I just keep them on task, pep talk them, motivate them, praise them, give them pointers. Most of the time there isn't a spare table for them to gather round so I work my way round the tables. Some children who have SEND may be sat on the table nearest the front but there are other children on that table too. Classrooms are tight because everyone sits around a table rather than in rows.
Work is differentiated and so higher ability children are challenged and that is the name given to the questions. So in maths everyone has to complete say the first 5 questions and get their work marked to ensure they understand the concept before they can move on. Children do work at different speeds and most move onto the next set of questions and some children probably about 5 or 6 in class will have moved onto the final set of questions.
For marking the children put their finger in air for the first set of questions and a finger and thumb for the second set meaning we can prioritise the children still waiting for their first set to be marked.
There might be ability tables in year 6 when some children need more help. But my experience in the last 12 years has been mixed ability and some children move seats for maths or English or both.
What I can tell you is that learning is not linear, no one is going to ask what table you were on when applying for a job when they are 30. In all honesty a lot of it doesn't matter. What does matter is parental involvement, nailing times tables, spellings and reading, whether reading to them or them reading themselves but asking questions of them about their book for comprehension. Plus once primary is over there is no standing in the school playground with other parents. It is bliss.