I would advocate making science classes metric only - however I would support having imperial in Maths and English.
In my opinion it would be a mistake to limit metric units to science classes - this would only reinforce the impression in America that metric is something for scientists only, rather than the normal and natural set of units for everyday use.
Don't forget that measures do make up part of the language and denying a new generation while the 'one above' converses freely using a mix of measures would leave kids confused. Nothing pro-imperial or anything - just common sense because kids would have many questions unanswered by school.
In Ireland, schools started teaching metric only in 1970 - the year I entered the secondary school system (high school). All text books (including Math, English & Irish books, apart from literature texts) were converted. There was no problem not understanding older people talking about measures. Natural osmosis ensured that youngsters got an impression of how big a mile was, or how tall a six foot person was, even if they didn't know how many ounces there were in a pound, or yards to a mile. As for English class, old units were treated in the same way as references in literature to leagues, pennyweights, gills and fathoms - former units of measure that have been superseded.
The important thing was that they got to think in metric, and thereafter viewed imperial measures as a peculiar and awkward leftover of a previous age. In later years, they would never have any feelings of sentimentality towards them, which helped ensure a nearly universal acceptance (even relief) as imperial units slowly disappeared.
It is important to note that it took 20 years from this start to get to the point where imperial units could disappear from road signs and shop labels without controversy. During the interim, there was no communication gap or confusion between youngsters and older people.
I suspect that is the reason why imperial made a return to the curriculum in the UK from the 90's (when I was at school in the 80's I can't remember being taught any imperial, although I can imagine teachers 'spoke it' so to speak).
I believe the real reason was that those who were anti-EU successfully linked metrication in the public mind with European integration (despite the fact that metrication was initiated as a British Commonwealth wide project). Thus retention of these units became part of defending British culture, rather than ensuring that British people and industry could enjoy a better tool by which to conduct commerce. Pupils have since paid the price in terms of additional baggage they have to endure in schools.
By all means teach both sets of units if your desire is to end up with the mess of units used in the UK, but if you want to lay the foundations for a complete transition in the long run, international experience would suggest removing them completely from the classroom as soon as possible.
Tom Wade
