Report effect size?

I am new to this forum and my knowledge about statistic is pretty basic. So beforehand I thank you for your help.
In my research I used non parametric tests to compare two groups´ academic performance. It had a quasi-experimental design where the groups were not randomly selected but were real class groups.
A question arose in my mind: should I report the effect size? I was told that the effect size is recommended when parametric test are used, is that correct?