Children in general are intuitive able to differ between contexts. This means, they are able to differ between parents using different languages, houses with different rules (parents, grandparents, school) and also if they live without a second language, they would use words with their friends, they would not use at home.
So you can trust your child to differ between reading at school/kindergarden and reading at home. Maybe there will be a transition time.
As an example my son was (newly) 5 years old, when he started in a english school. Both parents are German native and my son had not spoken one word english before.
While learning the alphabet and the sounds, we had discussions at home about the letters and how their sound is. So I invented some "names" for 2 or 3 most troubling letters (english "e" sounds as german "i" - we called one "the snail" and the other "the one with dot" to clearly differ in descriptions).
At home my son read not much in the beginning. Sometimes I gave him the notes for shopping and he read to me "Brot"(bread), "Äpfel" (apples) and so on. In school he learned reading in a regular manner. Sometimes we discussed the differences, when he got a question (ie special letters as ä, ü or ß).
But he adores me to read loud for him and I did and do so in german (95%).
In principle 80% of books he owns are in german language. So when he reads, he reads mainly german in his free time and english at school. He is 8 years old now and reads both languages fluently. More struggle is in the writing, but the reason is simple, that he uses english sounds to write german words, because he has less experience in writing german texts than english texts. But then he asks me "how is the german letter for this sound?".
For me the conclusion is, that if you have clear context, children are able to switch between languages. ((nearly) all at home is one language, at school the other) and to find unique "names" for unclear differences (german i and english e sound the same, so use names to differ clearly).