STUDENTS in Macau are suspected of making and planting a bomb at their school which shattered windows but injured no one. No arrests were made after the explosion about noon in a classroom of the Catholic Yuet Wah College's English Section. Students in theclassroom said there was a bright flash followed by a bang. Police and ballistics experts rushed to the scene. A police officer said he believed the device, roughly made with gunpowder and a clock, had been made by the students. School officials refused tocomment.