I think there is a great deal of difference between private schools and even people who set up schools with the best of intentions make ghastly errors of judgement. I think languages should be taught in primary but not at the expense of basic literacy and numeracy.
In my DD's private primary school (a few years back now), they were taught Latin, French, Italian and Spanish from Reception. With the exception of Latin which was taught by the proprietor, the others were exceptionally badly taught by an Italian speaking former nursery teacher who had no proper qualifications. For example I saw a French worksheet that the teacher had prepared and the nouns had the wrong genders.
They were also taught critical reasoning from the age of 5 which went right over their heads. My DD2 was not able to read properly at the age of 7, but the school rubbished the idea of dyslexia which she was later found to have. When she started state school in year 4, the Head told me she reminded them of children they had seen, who had never been to school.
DD1 was judged to be about 2 -3 years behind in maths when she started at her super selective. Luckily maths was not in the entrance test or she never would have got in.
I shudder when I read that Gove has told academies that they don't need to employ qualified teachers, while there are exceptions, we were badly let down by so called teachers being completely unfit to teach but presumably cheaper to hire.