In a world language classroom, how do you determine how much L1 to use yourself with A1-A2 level middle school students?

I teach English to French middle schoolers in France. I'm part of an extra-curricular program in English that the kids families pay extra for. The school wants me to teach only in English. I tried that last year, and found that I had some discipline problems and suspect it hindered progress. I do try to keep the kids speaking only English in class. I'm looking for advice on how others determine how much L1 to use with the students and in what circumstances.

Thanksin advance for sharing your wisdom!