Some can learn tables. Some can't.

Some can learn tables.
Some can't.
Some can use the tables and understand maths.
Some can't.
You can know the tables and be good at maths.
You can know the tables and be no good at maths.
You can not know the tables and be no good at maths.
You can be no good at tables and be good at maths.
Knowing the tables is not the be all and end all of maths.
Maths is more than tables.
If you have a high stakes test on tables, you end up saying to children that maths is knowing the tables.
You end up saying to them that the most important thing about maths is knowing the tables.
Giving them a high stakes test which will judge the child, the teacher and the school, will add one more stress to education.