Les portes sont ouvertes,
Les portes sont fermées
The doors are open,
The doors are closed
This song doesn't make sense unless you know that it originated as an Occitan song which says "Pass by the bridge, little carts". The song passed to the French with what words sounded nearest to the original ones, hence "pel pont" (by the bridge) became "pompons" (pompons/bobbles) and "carrilhons" (little carts) became "carillons" (chimes).
A leader is chosen. Two children join hands to form an arch and sing the song, while the other children pass under the arch in a line. On "clé", the two children forming the arch bring their arms down on the child passing under the arch. The leader secretly asks him/her a question ("Where do you want to go? Bordeaux or Marseilles?" "Will you cross the bridge or jump over the brook?"). The child must secretly answer and according to his/her answer, lines up behind one of the two parts of the arch. When all the children have been caught there is a tug of war to decide which side is the strongest.
Thanks and Acknowledgements
Many thanks to Monique Palomares for contributing and translating this rhyme.