Independent schools are generally academically selective, using the competitive Common Entrance Examination at ages 11–13. Schools often offer scholarships to attract abler pupils (which improves their average results); the standard sometimes approaches the General Certificate of Secondary Education (GCSE) intended for age 16. Poorly-performing pupils may be required to leave, and following GCSE results can be replaced in the sixth form by a new infusion of high-performing sixth-form-only pupils, which may distort apparent results. On the other hand, pupils performing poorly cannot legally be excluded from a state school solely for poor performance.