I did really badly at exams.

[tufguy]

I did pretty well at exams

I did really badly at exams.

I didn't do well when I was at school.

I didn't do well with my academics.

I did pretty badly with my academics.

Please check my sentence.

 

[tedmc]

I would use "in my studies" instead of "with my academics". The rest is fine.

 

[emsr2d2]

Sentence 1 lacks a closing punctuation mark.

 

[Rover_KE]

... and for the second time, sentence should be sentences.

 

[Tdol]

I would use "in my studies" instead of "with my academics". The rest is fine.

With my academics does not work. An academic would be your university tutor.