"Disappointing" refers to the results, not to the person. The results are disappointing. The student is disappointed. The word "got" means "received", and it also refers to the results. This is different from "got" meaning "become", as in "I got confused". I got [disappointing results] or I was disappointed [ by the results]. NB This is exactly the same as all the other pairs of adjectives formed from verb participles. For example: I got [some exciting news] I got excited [ when I heard the news].

Hi Kyouko! The problem here is that the verb "to get" (got) can have different meanings. It can mean: 1) "to become"; or 2) "to receive". In the sentence "I got disappointed" it means "to become" and it describes your feeling. For example, you would say: "I got disappointed... because the result was bad." (I became disappointed because the result was bad). If you say "I got disappointing results", the verb "to get" means "to receive" and the word "disappointing" describes the quality of the result. "I got... disappointing results" (I received a result that was disappointing). I hope this helps!