I think Siemens have put together an excellent example of an on-line course on this page.  There are a number of free courses available.  I followed the Basic Electricity course as that would be the starting point for my students. 

Basic Electricity is broken down into sections titled:

• Introduction,
• DC Circuits,
• Magnetism,
• Alternating Current,
• Reactance,
• Impedance and
• AC Circuits.

Each of these units is again segmented into smaller parcels then presented a screen at a time.  When you have completed all these units, a final exam is provided, and a 70% pass will allow you to print out a Siemens Certificate.  Each unit is supplemented by a downloadable PDF to facilitate further study.

The pages of each tutorial are concise allowing rapid loading.  Each new idea is illustrated with an explanitory drawing. Learning material is expressed in simple terms, and allows the learner to take it all in, a point at a time, and progress to the next frame.

I would highly recommend this site for use as on line learning material for > year 9 students, and perhaps as a model for future similar presentations.