Cornish dialect
When Cornish people started to go to school in the late 19th century, teachers told them to speak 'proper' English not dialect. A lot of people thought that people who spoke the dialect were not as intelligent and educated as those who spoke 'proper' English, so people spoke the dialect less, and the dialect declined. In the 20th century, a lot of people moved into Cornwall from the south east part of England near London. These people did not speak the Cornish dialect and found it hard to understand Cornish people who spoke it. The Cornish people spoke the dialect less because they did not want people not to be able to understand them.