Is there any software intended to allow 'detailed control' on how each student can use their PC? I don't mean something that's pre-configured by an ICT administrator to (say) block or allow access to particular websites - I mean something much more fine-grained control than that, and something that can be changed/configured by the classroom teacher at the start (or during the course of) the lesson. [I feel I need to resort to this because of too much mis-use of the PCs during lesson time - especially students accessing their own favourite websites whilst they should be completing the set task. I know the counter-arguements, eg. that students need to be given the freedom to make their own mistakes, or that it directly goes against the fundamental idea of a PC as a general purpose tool, or...., but... Also, I prefer to have sanctions that 'fit the crime', and giving lunchtime detentions or whatever for mis-use of the web seems 'wrong'. I much prefer a solution along the lines of 'if I can't trust you to use this tool appropriately, then I'll dis-engage some of its features'.]. For my purposes, all I need is something that (after some initial configuration for the network IDs of the 'managed PCs') allows me to: - control precisely what applications can be launched at any given time. - control precisely what URLs they could visit in the course of the lesson. - *ideally*: allows me to quickly apply these controls to just a few selected user accounts, rather than necessarily the whole set of machines. That way, most students I would 'trust' to get on with the core task (but would still be allowed to 'mis-use' the PC if they, occasionally wished) and have unrestricted use : but I could quickly target (in a very controlled manner) those whom (behaviour shows) I could not trust. I'm sure some such software must surely exist because it surely has an almost global market (in schools, maybe even businesses, throughout the world). Is it affordable for schools? Is an open-source (i.e. free) version available?!! Not asking for much am I?