DAR ES SALAAM, June 25 -- FOR many successful entrepreneurs the journey begins with a simple observation that later grows into a life-changing idea. For Esther Kelvin, popularly known as Essy Fashion, that defining moment came while she was still a secondary school student.

Today, Esther is a wife, a mother and the Chief Executive Officer of Essy Fashion. Yet long before she built a fashion brand or led a team of designers, her story had already begun unfolding quietly in the most unexpected place, a school uniform that did not feel right to her. “I started sewing when I was in Form One,” she recalls.

What first pushed her into tailoring was not formal training or influence from a family member, but dissatisfaction with what...