AN 18-year-old schoolboy escaped serious injury when he plunged 15 floors from his flat in Kwun Tong yesterday. Police believe Lam Wing-shun survived because he hit a second floor tin-sheeted canopy before landing on the podium of the Hip Wo Street building. The sixth former even tried to climb down from the dented, three-metre square canopy by himself, but was told to wait for an ambulance. He was admitted in fair condition to the United Christian Hospital. After the youth was given oxygen in the ambulance he was able to tell police that he had jumped because he was depressed. When police later went to Lam's home, they found his 20-year-old mentally retarded brother, who had overstayed his two-way permit. He was taken to Kwun Tong police station, where he was detained pending repatriation.