Is there any chances that septic shock caused by streptococcal infection can cause brain damage in a teenage boy?

Depends. Septic shock will not usually cause permanent brain injury, but there are exceptions. One is if the infection directly involves the brain. So strep pneumoniae can cause an infection of the lining surrounding the brain (menningitis) that can result in brain injury. Sometimes if the shock is severe enough with blood pressure very low for a long time, this can result in brain injury. This is unusual.
Unusual.... ..In septic shock, the brain is usually spared; loss of fingers and toes, and kidney damage, are far more common.