There are huge conceptual difficulties associated with electricity – even among professional physicists you will hear debates about how to interpret circuit behaviour. It is therefore important for teachers to be clear about what it is they are teaching. Some of the issues are discussed in more detail at: http://www.eskimo.com/~billb/miscon/whatis.html
Both the 3rd and 4th class and 5th and 6th class units on electricity set out to reduce as much as possible the difficulties presented by new terms and scientific vocabulary. The units also have examined carefully the number of concepts which are introduced at each level.
The key concept is that electricity can be viewed as a flow of electrons, called ‘tiny particles’ in the modules. Electricity is not ‘power’ and it is not ‘energy’.