According to the Telegraph (link below) more than 1 million school students in the UK speak English as a second language. This means about 1 in 6 students on average with about 1 in 8 at high school. In some parts of London about 75% of pupils don’t speak English as a first language.
This is putting a huge strain on the system where teachers specializing in ESL aren’t always available.
For more, see here.