Why did the mufti try to close the Kushal School in I Am Malala?

In her autobiography, I Am Malala, young Malala Yousafzai describes her upbringing, family values, and Pashtuni culture in Pakistan. The events of her life take place in the backdrop of Islamic extremism and the sociopolitical horrors of her region, the Swat Valley.
What is very unique about Malala's family is that her father, Ziauddin, is passionately devoted to the establishment of equal rights for girls and women. Although the family was eventually forced to relocate to Birmingham, England, for many years her father was the principal of the progressive Khushal School, which allowed children of all social ranks to attend. He founded this school himself, with the hope of providing equality in educational opportunities.
Ghulamullah, a mufti (Islamic scholar) in the community, tried to have the Khushal School closed because girls attended as well as boys. According to the extremist interpretation of religious law held by the mufti, girls were supposed to be kept at home.
Eventually, Mufti Ghulamullah and Malala's father, Ziauddin, reached a compromise. The girl students were to enter through a separate gate where they would not be seen by men.