The purpose of this study is to evaluate the efficacy, safety, and tolerability of 3 weight-based, fixed-dose groups of paliperidone extended release (ER) compared with placebo in adolescent patients between 12 to 17 years of age, who are diagnosed with schizophrenia. Paliperidone ER is an atypical antipsychotic agent approved by the U.S. Food and Drug Administration for the treatment of schizophrenia in adults. Patients may be voluntary inpatients or outpatients at the time of the screening visit, but should have returned to their usual living situation by Day 21 of the double-blind treatment phase. The study duration is approximately 10 weeks. Patients who have completed this study or who were discontinued from this study due to lack of efficacy but have completed at least 21 days of double-blind treatment and are expected to benefit from paliperidone treatment, may enter an optional open-label safety study.