Abstract : In school, the information search on the web (ISW) assisted by the search engines play a growing role in teaching and learning. But if the students do a lot of ISW, there are few studies on the high school students; we do not know how they do the ISW and what approaches they follow. The ISW is varied according to the search context and the situation met in the search process itself. Two tests with several search tasks defined by the researcher were passed with 79 vietnamese high school students. If they report only partially ISW of the participants, they allow to register the approaches used, making the hypothesis that the approaches implemented have some stability.In trying to simplify the ISW of the participants, a general schema of ISW is designed with five elementary search actions identified: reading of task, formulation of queries, consultation of page of results, reading of web page and notation of answers. This schema allows to visualize characteristics of ISW of the participants: search engines are the main tool; the search uses more the formulation of queries than the web navigation; the pages of results are the center of the search; the web navigation is made from the pages of results is rather in breadth-first and according to the model "Hub and spoke".By focusing on the queries, four elementary approaches of ISW are recognized: top-down, bottom-up, specific and general. The participants tend to use a specific elementary approach for a closed task; a general elementary approach for an opened task. When the task is difficult, the participants tend to change more often their elementary approaches during the search and to use more processes, tools and more search techniques.During a period of two years between two tests, we notice changes of behavior of the vietnamese high school students: the increase of the belief in the reliability of Wikipédia, the use of Wikipédia as a search tool, the use of the options of translation of Google and the increase of queries in English; the decrease of the use of quotation marks, Boolean operators in the writing of queries.