A teacher was in hospital last night after a chemical bomb thrown by a student at Figtree High School exploded in her face.The disturbing incident came three days after a muck-up day rampage on Monday, when Year 12 students reportedly donned clown masks and tore through the school, throwing water and flour bombs and threatening staff and peers.A staff member, who did not wish to be named, said staff and student safety had been put at risk."I look at the violence the kids get away with - we're under siege at this school. [Staff] are so upset this happened," the source said.In yesterday's incident about 3pm, a drink bottle filled with a liquid chemical - believed to be chlorine - was thrown from the gymnasium's mezzanine level onto the floor below.A female teacher in her 50s picked up the bottle, believing it to be water, before it exploded in her face. Paramedics were called to the scene and treated the woman for blurred vision.She was rushed to Wollongong Hospital and was in a stable condition last night.Students who contacted the Mercury today claimed a Year 10 student was responsible.In the Monday incident, about 60 students, some wearing clown masks and white overalls, reportedly rioted through the school for two hours from 9.30am.Two Year 8 girls were allegedly wrapped in plastic before sex toys were hurled in their face.They have since been spoken to by the school's welfare officer."[The students] were throwing water, flour, vinegar, stink bombs - there were kids jumping out of classroom windows," the staff member said.One teacher reportedly slipped over and injured her knee in the panic and a student suffered a chipped tooth.Year 10 students sitting their trial School Certificate were disrupted when objects were thrown at the wall of their exam hall, the staff member said.Staff called an extraordinary meeting in the days after Monday's rampage and asked why police were not immediately called."We are all disgusted … no lockdown was called. The bell went, and kids were released into this mayhem," the source said.Police were investigating both incidents, an Education Department spokeswoman said."The [department] does not tolerate any 'muck-up' that involves illegal activities or antisocial behaviour, and students found to have been involved will be disciplined accordingly," she said.The spokeswoman said the decision to place a school into lockdown was made at the discretion of the principal, and she denied Year 10 exams were disrupted."It is unfortunate that a minority of students' actions negates the good work and positive actions of the majority of students," she said. DO YOU KNOW MORE? Email us at scoop@illawarramercury.com.au or phone 42212207