My son had 4 years of french at primary, but in year 7 he is only national curriculum level 2. In primary he did no writing and the standard of french of most his primary school teachers was not good enough.
This clip shows what is possible with ambitious high quality teaching. Its amazing to see small children writing in manderin.
www.bbc.co.uk/news/world-asia-24672295
I would love my daughter to attend a bilingual primary. Prehaps we need careful thinking about the most useful language for a British child. Prehaps my daughter could have a properly qualified French teacher teach one day a week in a primary school. The children could learn though maths, art, geography, history, PE, RE lessons taught in the target language.