I have experience teaching with this age group. It can be difficult to turn things around when children become accustomed to disrespecting rules and being allowed to do what they want, rather than what is expected of them. But, don't lose hope. Naughty children are the best kind because they present the largest challenge to teachers. If a teacher can master this type of child, the gift of accomplishment and true success is amplified.
It is easy to become frustrated in this situation. One suggestion to "turn things around" is to make a plan for change. I find it best to make lists. Write down your goals, write down the childrens goals...are there any in common? Find some...read between the lines. Decide what you expect and make a strict schedule that is realistic for both you and the children to adhere to. When I say strict, please keep in mind that these are small children and can only learn through PLAY. Anything that is not fun and engaging will lose their attention in 5 minutes or less.
Physical activity should be incorporated if at all possible, especiallly when you notice "ansy" behavior or an urge for activity. Activities should alternate every 30-40 mins depending upon the children's interest level. Even if they are having fun it is a good idea to stop the activity and keep them on the sched. This reinforces the idea that YOU are in control. They will be eager to repeat the activity the next day. Use resource materials to get ideas for fresh learning games.
When you have completed the activities planning stage. You need to make a visual change as well as an attitude change and sched/activities change. These changes should occur simultaneously. Don't surprise the children, let them know the day before that there is going to be something NEW and exciting! Redecorate the room, or change your apparel even. You might have fun (and get a lot of attention) by wearing an unusual hat or tie, but don't be rediculous. Tell the children, when you are wearing your hat it is time to be serious. You can take it off when it is time to relax and be silly. Make sure the children are rewarded for their hard, serious work with a few minutes of "silly time" in between learning activities.
If they are able to SEE this visual change, they will associate it with your change in expectations. You MUST communicate to the children what is expected and also what is NOT ALLOWED. Children (even naughty ones) will rise to the occasion if you tell them you need their help, so give them responsibilities. Make them feel important by giving praise at any opportunity to reinforce correct behaviors. At the same time you must not allow behavior that is disrespectful to you. Set limits to protect your sanity. There must be a consequence when rules are not followed. These expectations should be posted and reviewd occasionally, if not daily. Always reward desirabe behavior and ignore undesirable attention seeking behavior that is not in clear violation of the rules or dangerous.
Children at this age level are not really at all interested in learning a foreign language. It's the parents desire. If you can help the children own that interest, you might increase your success. Introduce a beloved American or English speaking character through story. A famous sports champ, or cartoon character. For example, 'Barbie' is popular with little girls. If the children identify with or admire someone who speaks English, it could develop into an interest.
Use this as a rule of thumb, if you are comfortable and having fun, most likely the children are too, if not...well, you know. Use your own feelings and anxiety level as a gauge for what needs to happen next.