Short answers, pulled from the story.
The King's School Canterbury was founded in 597 with the singular purpose of teaching Latin to future priests and monks. These earliest institutions attached themselves to cathedrals and monasteries to focus almost exclusively on the language of the church.
Christ College Brecon was founded in 1541 and the Friars School Bangor was established in 1557 as examples of the oldest extant schools in Wales built upon former Dominican monastery sites. The Crypt School Gloucester was also founded by John and Joan Cook in 1539 to illustrate this pattern of endowment creation.
State-maintained grammar schools reached a peak in 1964 with 1,298 existing in England and Wales. Direct-grant grammar schools numbered 179 and took between one quarter and one-half of their pupils from the state system while accepting fee-paying parents for the rest.
Some areas like Buckinghamshire Kent and Reading maintain formal grammar school systems where the eleven plus exam identifies around 25 percent suitable for grammar education. A University College London study showed UK grammar school pupils gain no significant social or emotional advantages by age 14 over similarly gifted pupils in non-selective schools.
The Tripartite System largely abolished itself in England and Wales between 1965 and 1976 through Circular 10/65 and the Education Act 1976. Most maintained grammar schools amalgamated with other local schools to form neighborhood comprehensive schools though some counties successfully resisted conversion.