Agreed that an adequate, clearly understood but concise brief (God forbid we ever get to the stage where we have to write reams after each lesson - keep the insurers away from this thread!!) should be written up at the end of the exercise and I attempt to do this on each and every occasion but have to admit sometimes it has to wait until the end of the day. For that reason I have made up a simple form that I use for every flight, on which I write Start Up, Brakes Off, Take Off, Landing, Brakes On, Shut Down times, as well as details of a/c, clearances, student, observations and a/c tech problems. It's not perfect and I'm sure it can be improved on. It's sufficient for me that even if I couldn't write up the student records at the end of the flight I can sit down at the end of the day and catch up then. If anyone wants a copy, drop me a PM with your e-mail address and I'll fire it off asap - feel free to butcher it to your own needs.
Life's A Beech has touched on the fact that student records, without doubt, contain information of a personal sensitive nature, i.e. the student's personal details, and are therefore subject to the requirements of the Data Proctection Act 1998, which gives the student the right to see and take a copy of his/her records at any time, subject to payment of the appropriate fee (£10 maximum at the last count).
There's nothing wrong with making negative comments provided you are able to professionally qualify those comments and we should all be able to do that. However, I would be extremely careful of making comments in a record that could be misconstrued and used against me and/or my employer.