We would like to follow the progress in students’ learning through the development of their mathematical skills and are looking thus for an appropriate classification of learners related to their achievements.
Your question is quite vague, however, it reminds me the analyses performed within the so-called "Rasch Analysis" or "Rasch Model"- it is quite broad theme, but maybe my hint will be useful for you.
Dear Michal and Peter, thank you both for valuable recommendations. To explain better what we are looking for, let me give you a simplified example. Assume that we have students in the maths class who score, respectively on a number of tests rated, say, on the scale 1 (lowest) to 5 (highest) as follows:
#1: 2, 2, 3, 4, 4, 4, 5, 4
#2: 3, 4, 3, 4, 3, 4, 3, 4
#3: 2, 3, 4, 3, 2, 3, 4, 2
How would one classify their learning progression/achievement/success, if at all?