Student or Learner
should I say
I am good at very school subjects or IN ....?
I'm not a teacher
Here's what I've found on BBC - Learning English:
Lim Chiu Lan from Malaysia asks about prepositional phrases: Would you be good enough to explain to me what is the difference between these prepositional phrases: good at and good in? Which of the following is correct: 1) 'I'm good at English' or 2) 'I'm good in English' and 1) 'I'm good at football' or 2) 'I'm good in football'?To be 'good at' and to be 'good in' are often interchangeable, Lim, and there is no easy rule to follow. In simple statements, like the ones you have quoted, the standard form appears to be 'good at' as in
- 'I'm not very good at football'.
However, in this following sentence, to be 'good in' seems more likely than to be 'good at', i.e:
- 'He was the best in the class in French, but in mathematics and chemistry he was not so good.'
This is perhaps because with other expressions or verbs denoting assessment or ranking, the preposition in would be required, thus:
'In pharmacology she obtained/scored/gained/attained the highest marks.'
There's similar information here: Grammar Exchange. Extracts below:
Good at [language] expresses proficiency...Good at describes the way in which you DO something.
Good in describes how you perform in a school course.You can say "He is good at English." This means that he speaks English well.
You can also say "He is good in English." This means that he does good work in English as a school subject.
"”He is good at math (He is good at doing math)
"”He is good at tennis (he is good at playing tennis)
"”He is good at cooking (He cooks well)A person who is studying English as an academic subject is good in English, just as a person who is studying physics is good in physics. In English implies that the person has a high standing in classes, indicated by good grades.