122: Q&A - How to encourage a reluctant child to use the target language?

We are a Spanish couple living in a bilingual area where Spanish and Valencian are spoken equally. Our son is 3.5 years old. I have always talked to him in English since he was born. His father has talked Spanish to him. And he has been exposed to Valencian since he was 2 years old, first at nursery school and now at school. He understands everything I tell him in English but only on rare occasions does he answer me back in English. He says some words in English, but he’s hardly never able to build simple sentences spontaneously. I have used different strategies when he answers me back in Spanish. I usually repeat the sentence in English and then he says “yes”, but he doesn’t repeat them in English. In the last days I pretended not to understand what he was saying in Spanish to see if I could “force” him to speak English to me. But then he went to talk to his father and asked him the question in Spanish. Sometimes I think he is not getting enough exposure to English. He is at school from 9 to 5 and some days I only see him in the evening for dinner. There the vehicular language is Valencian and he gets two hours per week in English. My husband is also fluent in English and sometimes he speaks English to him at home. Should he start speaking English to him now regularly? At home or everywhere? Since both of us are Spanish it is a bit weird to speak English with each other. I teach English in a local high school and I feel confident with it, but I’m not sure if my husband could do the same. Our son has a good attitude towards learning and speaking English. His tales, cartoons and films are always in English and his bedtime stories too. We have planned a summer school in English for him to foster his exposure to English. During the last Easter holidays in which we spent more time together he started to say some short sentences in English such as “I’m ready” or “I don’t know”, etc. but now that he’s back to school he answers me back in Spanish again. Sometimes I feel like quitting speaking English to him, but I’m afraid he’ll lose all that he’s already learned. What can we do?