Good, Very good, very well, congrats! Excellent.

Estas formas estão erradas ou posso usar também?

Good, Very good, very well, congrats! Excellent.
You need / have to study more! You can do better...

MELHORE SUA PRONÚNCIA EM INGLÊS
Nesta aula, o professor Adir Ferreira, autor do livro "A Chave do Aprendizado da Língua Inglesa", nos conta como se tornou um Expert em pronúncia e dá várias dicas para você se comunicar melhor em inglês. ACESSAR AULA
2 respostas
Leonardo96 18 290
Em qual contexto? Só olhando assim, nao há nada de errado gramaticamente com essas formas.
PPAULO 6 48 1.2k
Seems like a follow-up question, following this one...
Cf. Como parabenizar por escrito um aluno no teste?

It depends, as I have pointed out, on several factors. The school rules, etc, the system/method that works for the teacher, whether or not the teacher favour (or have some time available) to oral communication (he would have some 'conference' with the learner, or those that need some special attention (lagging behind) etc.

One thing for a fact, comments should be (right) to the point, and focused on what could be improved about the (student) work. Careful not to be harsh to the point of crushing the student's spirit. Would need to strike a balance criticism x encouragement.
Such feedback (assessing) comments seems like being more a thing for writing assignments, not broadly used in exams/tests like in Brazil (I could be mistaken here, since I am no teacher, it's out of impression).

Anyway, adapting to Brazilian culture, yes, you could use "very well" or "good job" "It needs just some work on (your) prepositions, punctuation", etc.

Careful not make contradictory statements like: Excellent! But you need to improve grammar, puncuation, verb tenses, verb agreement!

Bear in mind that I am a layman (not a teacher) making forays on the realm of assessment. So my word isn't the last word on the subject. Let's wait for them to chime in and comment on.