Which type of school is characterized by selection based on academic ability?

Grammar schools are specifically designed to select students based on their academic ability, typically through an entrance examination known as the 11-plus in the UK. This selection process allows grammar schools to create an educational environment focused on more academically inclined students. These institutions aim to provide a challenging curriculum, enabling gifted students to excel and often preparing them for higher education.

In contrast, community schools generally cater to all students within a particular locality without academic selection. Free schools, while they may have specific educational philosophies or approaches, also do not inherently select based on academic performance. Religious schools can incorporate a variety of admission policies, but selection based on academic ability is not their defining characteristic. Hence, grammar schools remain the correct answer due to their clear objective of admitting students based on their demonstrated academic potential.