Was worried that I was losing my English after so many years abroad.
(Boring explanation: I teach students in France who are preparing for the competitive exams to become English teachers. Every year I spend ages correcting them and saying that it's "in line X" and not "on". Have just read the report on last year's exam and it says in sniffy tones that students really ought to have mastered basic constructions and know such simple expressions as "on line X", instead of all using the incorrect form, "in line X". While I am glad to be proved right on here, I'm p'd off at the report: do I now teach them 2 versions, one for use on the day of the oral exam, and one for using when they want to speak correct English?)
I would teach them the two expressions. For our German AL we were told to say "Ich habe Hunger" rather than "Ich bin hungrig" as the former sounded more Germanic and therefore would impress the examiner more.
However on the day my German was better than hers, 'cos my mum is German, and I learnt it over there on holidays and so on, so I needn't have bothered. But the principle stands, I think.