This study aims at investigating the difficulties encountered by public school students in Amman/ Jordan. The study raises the following questions: What are the obstacles that students may encounter in relation to the derivations? What are the causes of such obstacles? To achieve the aims of the study, the researchers manipulate two methods: A quantitative approach in which students of public secondary schools are tested and pre-tested in order to fulfil the reliability and validity of the results and a qualitative approach using interviews with teachers at the same secondary schools and one supervisor in Amman Third Educational Directorate (AL-Qwesmeh). The main results the study reaches can be summed up as follows: students are so poor not only in derivations and derivational suffixes but also in other linguistic topics. In other words, the problem of committing mistakes in derivational suffixes can obviously be regarded as being accumulative problem resulting from other problems which students are encountering in relation to, for example, parts of speech, word order or sentence patterns. Derivations and derivational suffixes should be taught in early stages such as the 8th grade or 9th grade rather than in the last ones like 11th grade or 12th grade.