The way I teach the computation of the Transition Level is to imagine you climb (with QNH set) and level off at the Transition Altitude (although fixed for a particular aerodrome it does vary across the UK - eg 3,000 ft for aerodromes outside controlled airspace, 4000 ft at EMA/BHX.....etc as published).
Just to add to that Bob, the way I teach is is to to tell the student to imagine we have parked the aircraft on a shelf at 3000 feet. we open the window lean through and observe 3000 feet on the altimeter, we than set 1013, now what is the altimeter reading without any aircraft climb or descent? From their pre-flight altimeter checks they should at this stage know, pressure up = altitude up and vicky versa. I find taking the CLIMB element out and parking the aircraft simplifies understanding