For one thing, almost all current teachers has no experience of programming. Other thing is the culture of teaching in Japan.
When you solve the problem by using a knowledge that isn't teached yet, the teacher said.
"You can't do that! You haven't been taught that yet!"
So, I can see the future where they say
"You can't use recursion! You haven't been taught that yet!"
Also, there is a seriously stupid culture in Japanese teaching.
Given a problem, "He went shopping and brought 6 candy bags which contains 3 candies each. How many candies does he have?"
The answer must be "6 * 3 = 18". not "3 * 6 = 18" The multiplication is not commutative. Because... I don't know. Some so called teaching expert who is the author of some textbook explicitly stated that.
(Actually, it must be 3 * 6 = 18 in original Japanese because, the word order of Japanese grammar requires to write like "he brought bag which contains 3 candies, 6." indicating this isn't even a math problem at all.)
That's why I worries about it.
As for Japanese isn't fluent in English even though we have mandatory English class, It's totally different reason.
School in Japan's English teaching is in fact bad. But that isn't the reason. If you're living in Japan, you have absolutely no reason to use English at all in your entire life. You can't improve language skill without actually using it.