It's possible that they are being obstinate. Or maybe they are battling us in a power struggle. But it is also possible that they are unwilling to risk failure.
Discouraged kids can demonstrate many different types of behavior–avoidance, belligerence, anger, and under the surface may be an unseen fear of failure. Clearly as summer approaches, there are lots of seasonal reasons to feel entitled to slack off. And, it surely is frustrating to parents because we have families to run, homes to take care of and a commitment to our jobs. The added stress of hearing "I don't wanna…" could be one straw too much.
If your kids are just being contrary with the upcoming promise of "three months' vacation", you need to stay firm to your family rules and structure. But, it might be also useful to imagine that they may be responding to feelings of discouragement.
Kids can be discouraged if they feel powerless. They can feel discouraged if they just noticed there isn't enough time in the school year to catch up or achieve acceptable grades. They can also be using "spring fever" or anticipation of summer to avoid blame for erratic moods or behaviors at home thereby deflecting attention from current challenges–like the end of this school year.
This is a good time to be on the look out for positive behaviors and productive choices so you can comment on them, praise them and promote more of them. If a child is in anyway fearful, now is the time to remind him/her that one-step-at-a-time is all it takes to begin a task.
"Take that first step. Bravely overcoming one small fear gives you the courage to take on the next." ~Daisaku Ikeda …and the same goes for any formidable or challenging task: choosing to take the first step makes it easier to take the next. And before you know it, you've achieved success.