This subject has now gone into 'thread drift' by the engagement of 'Warp Drive'. Everyone is entitled to their own opinion, however, the introduction of many 'if's and buts' doesn't/shouldn't sway opinion of good old common sense. Even if the student did pass his/her Skills Test it's not good practice to allow the euphoria of that event to, perhaps, thrust lack of concentration upon a newly qualified pilot to fly the aeroplane (solo) back to his/her airfield. It has been previously mentioned that a Driving School would not normally allow a newly qualified driver to drive the car after passing his/her driving test; for good reason! Psychological advantage has been quoted as being a good precursor to the Skills Test. I'd hasten to add that by authorising a return solo flight, immediately after the test, would be a psychological disadvantage in maintaining a modicum of safety and awareness. In my book that's called lack of 'Common Sense'!