The outing was part of a Medway initiative to improve test results by giving children real-life problems.
Fifty-six Year 5 and 6 pupils took the coach through the Channel tunnel to France, tackling maths problems set by Marion Browning, an advanced skills teacher. In Calais, they questioned French shopkeepers and cafe-owners about the euro. And on the homeward journey they stopped to buy tea and souvenirs - and worked out how much their remaining cents would be worth in sterling.
The trip was part of a longer maths-based project about currencies and countries which has included talking to the local MP and asking people in Rochester for their views on exchanging currencies.
Ms Browning said: "This brings problem-solving to life."