Relation between Attendance amd marks of students

I suggest you use a non parametric test of correlation since the data is likely to be ordinal. eg 'Spearman Rho'.
You will find details via Google.

Thanks for quick answer.
Some more explanation:
I have students attendance %age in one column and marks obtained in another column.
Regards

Yes. Since the marks are scores 'as judged by markers', they can only be classed as 'ordinal' data, and not 'interval data', hence choice of a nonparametric test to investigate correlation of rankings.

Thanks
I have checked in google.
I have a big data one class have almost 300 students and there are 3 sessions, so at least 900 pairs of data. Can I use this test for big data. Also please guide how to interpret this coefficient (rho)
Regards

Its a long time since I used this test so I'm not sure whether there are restrictions (probably not). But in order to reduce the work load you might be justified in collapsing scores into say 5% bands versus average attendances per score band. You are then only dealing with say 20 pairs of rankings.
Hope this helps.

Thanks for your time & sugession