Whether English should be taught in Japanese primary schools has been a controversial issue for many years. At present, Japanese school children don't read or write English in the classroom, but they learn basic English and Western culture while doing fun activities.
I think children should start learning English as early as possible, because they absorb knowledge like a sponge. It's wasteful not using their talent, energy and intellectual curiosity.
There are some Asian countries where English is used as a common language for historical reasons such as Philippines, Singapore and India. Children in those countries have benefited from it in the globalized world. I think Japanese children can also master English without difficulties if English were used as an communication tool at school.
Unfortunately, there's not enough school teachers who speak English fluently in Japan, so we won't be able to solve this problem easily.