MFL teachers, how much of the target language do you speak in the classroom?

I’m a student teacher and starting placement tomorrow. I keep hearing conflicting things from college and then from current teachers. Is it realistic to speak 100% of the target language in the classroom like college is telling us to? Co-op teachers say it’s not realistic and they speak in English a good bit. I’ll be doing the same since I have their classes, but just curious on this. Thanks for any responses