Complementing Sofía's answer. What she says is true, but... you have to take into account that if you say "ropa escolar" it will refer to the uniforms that kids use for school, which are very common in Spanish speaking countries in America. So, if you are looking for "ropa escolar" (meaning school uniforms) then you can say "estamos buscando ropa escolar (you can also say "uniformes escolares") porque pronto comienzan las clases" But if you are looking for clothes that are not uniforms, but that will be used to go to school, then you cannot sat "ropa escolar", then you have to say "ropa para la escuela" or "ropa para ir a clases".

We're looking = nosotros buscamos, but you can also translate = nosotros estamos buscando, because it's an action that we are developing. School clothes = ropa de escuela / ropa escolar. You can't say " ropa para la escuela", because the idea isn't clear, it can be understood that they are buying clothes FOR the school. The correct translation would be: " Estamos buscando ropa escolar porque las clases empiezan pronto ". In Spanish it's more common to say "empezar las clases " ( start classes ), and not to say " empezar la escuela" ( begin school ). Best wishes Sofía.

Esta perfecto, solo que quedaría mejor con el verbo en futuro: Buscamos ropa para la escuela porque empezará pronto.