Lots of interesting points here.
Singing, I would love to use the language skills in my school, but we are in a very rural area where my European heritage is the most exotic thing around! I am half German and married to a Frenchman. I do bring in any passing foreigner I meet; exchange students, au pairs, friends of friends etc.
The choice of language is often contentious, but in my LEA nearly all the schools chose French because the majority of teachers had learnt a little French when they were at school. There is also the problem of what happens at transition to secondary school; if half the children have reached Level 4 in French, does the secondary start them again at the beginning because the other half of the intake didn't do it at their primaries? (Sadly, in my experience, yes, leading to demotivation among some of my best students.) This could be a very good argument for a language not taught at the local secondary. The skills are the same.
It is also not the job of the primaries to teach the first bit of the KS3 curriculum. I would also be wary of teaching 'colours, numbers, greetings, common foods': that could so easily turn into an exercise in memorising lists. We teach songs, rhymes and games, reading story books, watch video clips and generally try to help the children answer the question "What would it be like to be a child in France/Germany/Spain?"
RomanHoliday, I quite agree that you can't teach a language in an hour a week. You can introduce an awareness of language and ideally a love of language, as well as teaching language-learning strategies which will be useful for the rest of their lives.