I am afraid I cannot offer any concrete advice than just this one:

From what you describe, the problem seems to be concentration. Maybe, some of the kids could be hyperactive.....

Why not sometimes taking the kids out for a walk or having class outside in an environment where they could use the English they know more spontaneously.
Language instruction in class always is a very artificial situation of actual language in use. We teachers very often tend to forget that!

Good luck!