Totally agree with Gooseberry's comments.
Kids seem to be "taught" too much too soon. My DC have been doing Whizz and they have been introduced to so many topics that I was in high school before I was exposed to them. Whilst it is great that they are aware of so many different aspects of maths, at times I think it is too much. Whizz is following the national curriculum so they are not learning anything they shouldnt be.
I am currently encouraging revision and drills of the very early stages of maths to ensure they fully understand the basics before they move on any further. But I am also finding that because there is so much, what do you focus on first.
Obviously addition, subtraction, multiplication and division is a priority. But then there are fractions, decimals, place value, rounding, properties of numbers, calculating numbers in your head, writing down sums and working out on paper (long/short, columns, etc), handling data - charts, graphs, mean median mode, probability, measures - time, km, cm, kg, ltr, etc., mass/volume, capacities, conversions, shape and space - nets, perimeters, areas, solid, 2d, 3d, being able to relate and understand word problems etc., to name but a few.
The list is endless, and you need to juggle lots of play activities into your daily life to be able to practice all these topics so they remember forever. If they dont practice, they forget