Kyphotic posture is not as harmful as long as it is not excessive & not progressive. The degree of spinal kyphosis matters. It's very difficult to predict it's progression & usually it progresses faster in puberty. Conservatively we can manage with specialized exercises like Schroth method which has been proven successful worldwide. Regular check ups with an experienced ORTHOPEDICIAN is also necessary to rule out it's progression. Sometimes if the angulation is more & rapidly increasing, we might have to use special braces like Milwaukee/Boston etc. Good luck!