Typodispositional layout and text architecture (Virbel 1985) play an important role in understanding and memorisation of instructions. Textual architecture may be signaled by linguistic marks or by the spatial organization of the text. In an experimental protocol, various versions of the same rule (exclusively involving linguistic marks vs. involving numerous typodispositional layout variations as titles and subtitles in bold, dashes, etc.) were submitted to reading, in order to compare the effects of these different versions on the understanding of the instructions, short and medium memorization and time necessary to find an information during the game. The results are significantly better with the most typodispositional one. The particularities of the school instructions are identified through an analysis of the linguistic and spatial organization of instructions in a grammar textbook for the end of primary school.