Studies have shown that electronic discussion can be used effectively to teach critical thinking and can achieve greater understanding. The use of online discussions is common in polytechnics and universities, and many schools in Singapore have begun to introduce online forums for discussion beyond the classroom. This research investigates lower secondary school students’ critical thinking in an asynchronous online discussion environment. The findings show that the students in this age group have only minimally exhibited critical thinking skills during the online discussion. However, investigation into students’ perception of online discussion shows positive attitudes. Some enhanced scaffolding strategies for online discussion participants and guides on designing good questions are recommended to foster critical thinking skills in this environment.