Elvora teaches the Cambridge curriculum: English, Mathematics and Science. All of it is taught in English, so your child gains the subjects and the language together.
That is a different result from an English course. An English class teaches English as a subject. Words are learned, tested and forgotten, because there is nothing to use them on. A child who studies English for years can still freeze when someone speaks to them.
Children who grow up with English never study it. They use it to count, to ask questions, to find out whether something is alive. When your child uses English in every lesson, it becomes natural in the same way.
Over a year that adds up to hundreds of lessons in English, and your child picks the language up naturally.