Best: I took 30 girls studying GCSE and A-level history to the Cabinet War Rooms in London two summers ago. The underground bunker complex was virtually deserted and it was possible to wander along the poorly-lit corridors for long stretches by yourself and imagine that you were transported back in time to those desperate and dangerous days.
The only reminder you were not alone was the tap-tap-tap of the tape-recorded typewriters and brief snatches of hushed and hurried conversations being conducted in pukka Forties accents.
The sight of an armed Royal Marine sentry suddenly shocked us out of our daydream. Many of the girls did not believe the figure was a dummy and expected to be jumped on as they carefully crept past holding on to each other for dear life. It was surreal to see Sir Winston Churchill's pyjamas folded neatly on his pillow and his slippers tucked under his bed in his spartan bedroom and it was fascinating to examine the massive maps where the prime minister and his staff plotted the ebb and flow of the war.
We walked to 10 Downing Street and were thrilled to discover that the Free Tibet Movement was staging a demonstration in protest at the Chinese leader's visit to the UK. The girls joined in with the chants of "Free Tibet - Chinese out" that echoed across the streets and they were bitterly disappointed when we had to leave.
Several of the girls were excited at the prospect of taking part in a full-scale riot but neither the demonstrators nor the Chinese Secret Service agents were going to be provoked by the antics of a gaggle of giggling school girls.
Worst: I helped to take 100 English as a second language (ESL) pupils from a summer school in Cambridge to London.
The teachers carried out regular head counts and roll calls as we shepherded them from Leicester Square to Covent Garden, but when we arrived, one of our pupils was missing. Pedro was Spanish, 10 years old and his English was so elementary that he frequently mixed up his hellos and thank yous. We left the pupils with two teachers and rapidly retraced our route, searching shops and side streets with the horrific thoughts of child abduction in our minds, frantically shouting out his name with rising anxiety.
We were about to call the police when we saw Pedro strolling down the street with his hands in his pockets and whistling a tune with not a care in the world. He had decided to play hide and seek in a shop but, after waiting for 10 minutes, he had got bored and decided to catch up with the group. "Dios mio. Donde has estado? Mezquino. Malvado (My God, where have you been?)."
Andrew Mackay is head of history at Brigidine School in Windsor.