Yes, it is dangerous. The long-term damages caused by sleep-deprivation are poorly understood right now, but we do know that extreme lack of sleep causes hallucinations at best, and psychoses at worst. With those things on the table, I suggest that you get 9-10 hours of sleep every night. That is the amount of sleep a growing teenaged body needs to meet the brain's requirements. Considering that your brain is not fully developed until the age of twenty-five, I think it would be very bad to screw up your brain with sleep-deprivation.