is this correct?

I suggest "All his classes were in English."

if you have to correct my sentence, what would you edit in it?

is it grammatically correct sentence and makes a sense?

Throughout his education, ... you need capital letters and the word "throughout" is one word, but this is otherwise okay.

"... the medium of instruction [in his classes] was English" (or you could say "the English language, with the "the" but there is no need to.) - However, no one I know would refer to "English" as "the medium of instruction. In-person classes, cyber classes, reco

which one is better? throughout his education the medium of instruction was english language ( or ) throughout his education all his classes were in english. ?

Since I pointed out that 1) you need capital letters, 2) that "the English language" requires "the" and 3) it's not a natural thing to say in the first place, and you ignored all of those points, I can't think why you bother to ask a follow-on question.

Which one is better to use ?

1. Throughout his education the medium of instruction was the English language.

OR'

2. Throughout his education all his classes were in English.

I would never say #1. I would only say #2.

These 2 are also correct?

a) Throughout his education all the classes were in English.

b) Throughout education all his classes were in English.

Use "his" in both places.