## 5 Discussion
### Study Limitations  
Despite the limitations that have been found in the study, the teams involved have reacted to minimize their impact on the material implementation. Many of the platform's usage limitations have been foreseen through previous research. Example of this was the continued support to teachers, who contacted the education team for the use of the material in the classrooms. Another damping effect was the fact that digital materials could be previously downloaded, prior to use, without connection in the classroom [47]. Should it be considered that in many occasions both implementation and usage processes are limited by the resources of the center: in some schools, there were devices available only for one classroom that were nevertheless managed to be used for all of the classes and courses. Another limitation, present from the beginning of the study in the selection of schools by the regions of Spain, has been the lack of required material, or abundance of obsolete devices, for the installation of the platform. In those centers that were able to introduce the materials despite the mentioned limitations, teacher training was always considered a key point. This training helped educators to integrate the content material in the classrooms, along with the additional managerial and support material provided [29], an assistance for teachers that can be reinforced to continue improving training on the use of digital resources.  
Similarly, in some classes, groups were identified by nicknames. In many of these cases, the average age of the students has been used to resolve the educational stage of the group; therefore, this has not constituted a significant problem except in a very limited amount of groups, which have been excluded from the study. Additional limitation during the study was that data were retrieved at a group level, instead of individually. While such input could prevent a more detailed study about the dynamics of each student, this did not cause any problem within the scope of the research and goals of this work. For future studies, we are working to design an assessment plan that allows the analysis of students at an individual basis.  
Because of the agreement between Smile and Learn and the Spanish regions where the educational institutions are based, we do not have full access to the academic records of the students nor to other internal academic information at schools, due to GDPR limitations. Although this information could be useful for further studies, it has not been required in this work, which is constrained to an analysis of the very platform's usage. For further studies, we will observe the possibility of extending this agreement. We are also elaborating a research proposal for recording more data regarding platform use with a Learning Analytics System in order to improve students' performance evaluation.  
Many platforms just evaluate via internal data, as this article proposes. In order to differentiate analysis from other types of evaluation, a control group should be launched in a school with which to compare the teacher's evaluation of students and grades. This part is however subjective for the teacher. Results obtained in games and quizzes show correct success rates and whether a correct usage is achieved. However, it would be necessary to develop more research about evaluative aspects, so that the correct successes in the activities of games or quizzes may correspond to evaluation standards. Likewise, the marks upon memory-driven results would be not enough. This makes the adaptation to an international evaluation framework a positive contribution to be able to approximate performance assessment to the required students' competences [32].