Microsoft Visio has a good range of electrical components even in the standard package. You can get an academic version pretty cheaply (£26 ex vat from Viglen). The advantage of Visio is that you can use it for all sorts of other graphics. I use it all the time at work, and when you get used to it, it is really powerful.
Alternatively you could download the free trial version of ICAPS from www.intusoft.com
, this is a full spice programme but has a nice graphical schematic builder that will allow you to build and model circuits with up to 20 components, that I assume would be more than enough for 11-18 year old circuit analysis.