Off to kindergarten! Starting school is a tremendous step forward in development for five-year-olds and often brings with it a disconcerting, but common, experience: nightmares.
Nightmares actually serve a developmental purpose: they balance the powerful aggressive feelings five-year-olds have with the helplessness they experience during nightmares. These dreams arise out of fear, aggression or strong wishes that they experience but can't yet handle. They are beginning to understand that they that they are smaller than adults. They no longer believe that wishing will make something happen. They want to conquer the world but realize they need help. The first months of school bring anxieties that are difficult for these former superheroes to manage. Their waking behavior may still include lots of superhero fantasy; they may be unexpectedly demanding or even have tantrums. These behaviors, along with nightmares, will decrease as the child is helped to manage their feelings.
Dr. T. Berry Brazelton, in his book Touchpoints: Three to Six writes, " Bad dreams appear to be inversely correlated with a five-year-old's ability to handle aggressive feelings. I urge parents to let up on pressure to be 'good' at such a time. A child of five is already working so hard to keep himself in bounds and is so worried about whether he'll succeed. Consistent limits, though, become even more important now."
When your child calls out during a nightmare, respond right away. Respond with reassurance and he will feel safe again. For example, ask him to tell you all the people in his dream, then put them in a box one by one and firmly close the lid. He will not be fooled that they are really in there (he is more mature now), but telling the dream will help him master his feelings. As he learns this skill he will grow in (real) strength.