At first, especially if you haven’t got much experience, it’s considered to be a problem. When you start, you always want a ‘Batxillerat’ classroom.
But once you are in a classroom and become aware of the different levels, the situation changes. It’s important that the group is aware of this difference as they can be aware of the difference of levels in Maths, Art and/or P.E.
There are some advantages to have a group like this in the sense that they can work together in spite of the differences, they can help one another in the classroom, and this can help the other students to be more confident with the language they are learning. If they are more confident, they are more motivated and the situation becomes better and more successful.