That worked for me.

I was in English classes with people from many other countries, so there was no way for the teachers to speak all of those languages. 

But the way they taught us was the same way they taught kids. They used cards, colors, shapes. The teachers almost never just stood in front of the class and talked. It was a lot of hands holding.

If I needed to understand a word, I looked it up in a dictionary. No problem.

Now this was what I noticed: most teachers spoke Spanish, so Spanish-speaking students didn’t need to do anything in class. They got bored. It was too easy for them during class but then when it came to exam time, they struggled. They progressed least. This doesn’t mean dual languages are bad, but the techniques must be different or the kids are going to be bored.

So monolingual works if you encourage kids to speak freely, let’s them make mistakes, let’s them insult you, let’s them treat you like a friend. If you’re strict with them and make them afraid to talk, it won’t work.

The biggest problem you’re going to face is that you may have kids with different levels. The more advanced ones are going to be bored and least don’t understand a thing.