When you have finished hacking the timetable around, use the ‘Double trouble’ routines to ensure you really have got a working timetable.  These will tell you when you have a teacher teaching more than one lesson at the same time, two lessons in the same room or a pupil scheduled for two simultaneous lessons.  This may be exactly what you want but, on the other hand, it may not.

There are checking options for staff, rooms and pupils.  In each case when you press the button you will see exact details of the problem.  Against each lesson where there is a, a coloured 'bomb' icon is displayed.  You can choose to replace the bomb with a smiley face if this is a known and acceptable double-booking. Simply click on the bomb to make it change to a smiley face.