This paper presents the Usability assessment of the Earth Course Large-Scale Technology Enhanced Learning (TEL) STEM education pilot, which is part of the European Horizon 2020 NEWTON project (www.newtonproject.eu). The pilot was carried out in two single-gender primary schools from Dublin, Ireland, where boys only participated in the first school and girls only in the second. Two experimental classes participated in each school. One group used the NEWTON-based lessons as an introduction to a topic (classes A with 30 boys and A' with 30 girls). The other group used the NEWTON-based lessons as revision on to the same topic, as they had previously covered the same content with their usual teacher 4 to 10 weeks earlier (classes B with 30 boys and B' with 27 girls). The Earth Course Large-Scale Pilot (LSP) includes a set of educational applications, developed as part of the NEWTON project in an effort to attract students to STEM subjects, which cover a set of topics within four main areas: Atmosphere, Geosphere, Biosphere and Astronomy. This paper reports the results of the usability evaluation for both schools. The majority of the participating students found the NEWTON-based lessons useful, particularly in classes that used it as an introductory tool. A comparison in usability between employing the NEWTON applications as introductory tools as opposed to revision tools was carried out for each school and grouping, showing that the classes participating in introductory NEWTON-based lessons provided higher usability scores compared to students participating in revision NEWTON-based lessons. It was also observed that the two boys' classes were much more open to using NEWTON-based lessons when learning, with the lowest scores received from the girls in experimental class B'. It was also reported by students, mainly in classes that used NEWTON-based lessons for revision, that they see it as a supporting tool for their teachers.