According to Mitchell's parents, he will be spending 6 months in Ohio. In the restaurant, when Jack tells Mitchell that "he's driving Nikki home", Mitchell responds by saying he's been there for 3 weeks, and in the next sentence tells Jack that he's leaving in 3 months. 3 month + 3 weeks = (not 6 months)
When Mitchell enters the flower garden, he has a helmet and elbow and knee pads, but when he enters the cave and comes back out, the padding and helmet are gone.
Early shots show the school grounds covered in snow. An when Mitchell first arrives in the classroom, you can clearly see outside the classroom windows and there is no snow on the ground.
At the end of the film, when Wiley is being driven in the back of the van, the ground is totally dry - when he jumps out in the next shot the ground is totally wet.
When Mitchell arrives in Cincinnati it is obviously winter and a lot of snow can be seen, as the film goes on it looks more like Fall then winter.
After his really bad day at school, Mitchell's aunt mentions his father had come down with Poison Oak. His parents are supposed to be doing research in Australia, but both varieties of poison oak are found only in the United States.
At the end of the race, Wiley appears to be suddenly wearing an aviator hat and no longer a helmet. However, Wiley was wearing the aviator hat under the helmet and has just removed the helmet.
When the family is driving home from the Airport, the reflection in Wiley's sun glasses never changes, suggesting the passing scenery was projected onto a screen.
In the final race scene, after Wiley is moving through the crowd, you can see a camera and crew quite visibly in the lower left corner.
During the skate scene, the beginning of the race shows them coming down Springdale Road - which is in Ohio, about 10 miles from Cincinnati. A few scenes later during the same race, the skaters are coming down Devou Park hill - which is in Northern Kentucky. The entire race scene bounces back and forth between Cincinnati, suburbs and northern Kentucky.