Gender bias in textbooks forms a stereotypical male and female character, thinking model, family role, and career choice, which affect students' gender consciousness, and ultimately affect students' gender roles.
Take a look at how genders are represented in textbooks. Are both males and females portrayed in non-stereotypical and diverse ways? Women and girls are given the same level of visibility and importance as males and boys. Consider whether the roles, accomplishments, and contributions of people of different genders are correctly reflected.
The Curriculum framework in general and textbooks, in particular, should be gender sensitive in terms of materials used, and the language used, letting equal participation of boys and girls in activities, avoiding gender bias, mainly gender stereotyping in the textbook contents, illustrations, and student activities, and evaluating gender integration in the curriculum framework are some of the aspects that have to be focused in the research of gender-sensitive textbook research.
It worth more to consider the existing social construct on gender responses and should be aligned within the internationally recognized gender based frameworks and better to proceed.
Issues of gender representation covers text and images so one good way is to consider this as absence/presence. What is marginalised, absent or absented (Bhaskar), what is magnified and what is narcotised or suppressed (Eco), and what space and frequency is given to each. So can be both qualitative and quantitative.
Also, consider the intersectionality of gender with race and class. If women/men appear, who are they? Also, if you are looking at gender in books in local and international languages then a comparison might help.