Why do children freeze when they have to speak English?
Speaking is the most exposed part of learning a language. In reading and writing there is time to think, and you can erase. In speaking, a mistake is heard at once, sometimes by the whole class.
School-age children already notice how they sound to others. A child who was laughed at once for an accent, or corrected in the middle of a sentence, quickly learns that silence is safest. It is not laziness and it is not a lack of knowledge. It is self-protection.
Does the silence mean my child does not know English?
A child who stays silent in English is usually not a child who does not know. Understanding comes before speaking, in a first language too. Many children follow questions and stories and know plenty of words long before they are ready to say a sentence aloud.
You can check this gently: ask a question in English that can be answered by pointing, with yes or no, or with one word. If your child answers correctly, the knowledge is there. What is missing is confidence.
Why is it better not to correct every mistake?
A correction in the middle of a sentence stops a child at the exact moment they dared to try. What they hear is not how to say it right, but that they were wrong. After enough of those moments, they stop trying.
Correcting every mistake also has a learning cost. A child busy avoiding mistakes uses only the sentences they are sure of, so they practice less. A child who allows themselves mistakes speaks more, and children who speak more improve.
How do you correct without marking it wrong?
The method English teachers use is to repeat what the child said, in its correct form, as a natural part of the conversation. The child hears the right sentence at the moment they are most tuned in to it, and nobody told them they were wrong.