This study examined the effect of learning in a computerized environment that includes simulations on the students' achievements and motivation, and is based on models that show that learning through simulation has more potential to promote the comprehension of abstract principles and concepts than traditional learning does. The theoretical background describes studies on technology in teaching, simulations and their role in teaching, learning motivation, and achievements. To examine the relationship between learning through simulation and achievements in the learning of operation systems in Information and Communications Technology (ICT) classes, we developed five simulations on a FLASH platform for each unit in the study program. The simulations were accompanied by interactive activity pages. This is a mixed-methods (quantitative and qualitative) research. The tools included preliminary and summary questionnaires. The sample included 151 high school students, who were divided randomly into two groups: experiment group--learned through online simulations (N=74); control group--learned without simulations (N=77). The findings indicated that students in the experiment group significantly improved their achievements. Also, integrating simulations in learning increased the students' motivation to learn ICT, and improved their comprehension of the study topics. The participants in the experiment group noted that learning ICT was important, and should be learned at school, as it is closely linked to their everyday lives.