In the theoretical part of the thesis we present phraseology, how it is integrated into the teaching of the Slovene language as well as other subjects, we discuss the causes of learning difficulties, how to recognize them, and what the characteristics of students with learning difficulties are. We look for the answers to these questions in the context of differentiated and individualized learning and learning assistance. When describing differentiated and individualized learning, we focus primarily on the types of work in homogeneous and heterogeneous groups. When it comes to learning assistance, we present a five-step model of providing assistance, which tries to address learning problems systemically and combines all forms of assistance into a whole. In the empirical part of the thesis we explore phraseology in traditional and contemporary fairy tales. Namely, we are interested in how common the idioms in the discussed works are, which parts of speech prevail, what the modifications, variants and changes of idioms are. We also observe the evaluative connotation, expressed with idioms. We control the understanding of phraseology with which the schoolchildren (nine graders) are faced in youth literature. Namely, we wonder if the results differ in relation to the inclusion in homogeneous and heterogeneous groups. We also observe how students evaluate the work and various forms of assistance in teaching Slovene in homogeneous and heterogeneous groups. The results show that the school should do more to promote the ability of meta learning, because students do not know exactly how to monitor and control their own learning and are not aware of their strong and weak points, so that they could compensate. When faced with learning difficulties, the students rarely search for learning assistance themselves. Mostly, their parents help them when in difficulty. One of the potential obstacles to solving learning problems is that the students seek assistance from experts when it is too late. For this we will probably need to change the point of view that learning difficulties present a problem and understand that seeking help is only a step forward on the path to success.