"got" and "marks" should be accepted as correct (at least if you're in Britain)

Unless you are dealing with a stative verb (no progressive sense - generally), the pretérito perfeito composto should be translated to present perfect progressive in English.

My son has been getting only good grades. or My son has been only getting good grades.

Listen, where I am from we say "makes good grades". "Making" good grades and "getting" good grades mean the same thing. It is a tragedy that such colloquialisms must be discriminated against and that we are marked down for putting such. My heart goes out to the developers of this course for having to read all of this garbage. Thank you.

Would the só have to come at the beginning of the sentence to make this mean: Only my son....

Well someone's feeling like bragging...

Is get the best translation of tirar? Would earn be a better one?

Am I the only one who translated tirar notas as "take notes"?

would "tem tirado so notas boas" mean something different? I feel like the "so" is place awkwardly compared to the English...

how can i increase my fluency on this thing. it says that i am at a %45 level. is it because i go from english to portuguese? I am fluent in spanish. if i went from spanish to portuguese would it be different? i finished the course and i only do the ones that i need refreshing on.