Tables should be well and truly known by now. Unfortunately this is very often not the case. Children need constant reinforcement and practice with their tables. Square numbers are also meant to be known, such as the square of 11. Knowledge of tables will help with most of these but not the larger squares. It is always a good idea to look at a tables square and note the way the square numbers take a diagonal path across the table.
Many children do not realise that the square numbers are the only whole number of squares that can be used to make a larger square (eg 49 squares makes a 7 by 7 larger square) and that it is not possible to make a larger square out of other numbers (eg 48 squares will not make a larger square, only a rectangle).
Free Y6 maths worksheet: Quick tables and square numbers (pg 2)