How many speak English?

I am 17 and my native language is English.
I fully realize that Japanese is spoken in Japan; but I was wondering out of the teenage population (specifically highschoolers) in Japan how many know any speck of English? and those who do know any English how much do they generaly know?

(remember, of the teenage/highschool population)

Every teenager in Japan is required to take English as a foreign language in school from junior high school through high school. Whether or not they can use it depends entirely on the individual.

I think you would be lucky if 10% of that age group actually SPOKE understandable English, and understood enough for you to talk to them.

I would say that even 10% would be optimistic. They all learn English, but not to speak it, so most Japanese people are not able to form complete sentences in English, however they know a lot of vocab.

"What's your name?" and "This is a pen" is the limit of most junior high schoolers and even high schoolers unless they have had a lot of private lessons or exposure to English overseas.

Learning english doesn't neccessarily mean they speak it.

They learn it because it is part of their curriculum, like math or history. You can learn algebra to pass the test, however it doesn't means someone wants to learn it, or remember it for actual practice use in their everyday life.