How to improve useability for non-native speakers who take English courses

Despite many attempts to get my 11 year old son to self-study with Khan Academy, he always complained that he couldn't read the questions. He is a good self-motivated student and performs well in math, science and Japanese, his native language. While he speaks English fluently he has never had formal education in English so there is a gap in his reading ability between the two languages.

Now, I found the perfect way for him to study on his own and he is loving it. I installed a browser add-on called "ImTranslator" which lets him see a Japanese translation of any word on-the-fly. There are probably other browser add-ons that do the same thing, but this one works well enough.

Lowering the barrier to getting quick translations of unknown words was really a game changer for us. I hope this trick helps some other KA students and parents out there.