How did the call for recognition of Bengali result to Bangladesh independence?

The Bengali Language Movement advocated the recognition of the Bengali language as an official language of Pakistan when Bangladesh was still a part of that country. Such recognition would have allowed Bengali to be taught in schools and used in government affairs.

When the state of Pakistan was formed in 1947, its two regions, East Pakistan (also called East Bengal) and West Pakistan, were split over cultural, geographical, and linguistic lines. In 1948, the Government of Pakistan ordained Urdu as the sole national language, sparking extensive protests among the Bengali-speaking majority of East Pakistan. Facing rising sectarian tensions and mass discontent with the new law, the government outlawed public meetings and rallies. The students of the University of Dhaka and other political activists defied the law and organised a protest on 21 February 1952. The movement reached its climax when police killed student demonstrators on that day. The deaths provoked widespread civil unrest led by the Awami Muslim League, later renamed the Awami League. After years of conflict, the central government relented and granted official status to the Bengali language in 1956. (In 1999, UNESCO declared 21 February International Mother Language Day, in tribute to the Language Movement and the ethno-linguistic rights of people around the world.)

The Language Movement catalysed the assertion of Bengali national identity in Pakistan, and became a forerunner to Bengali nationalist movements, including the 6-point movement and subsequently the Bangladesh Liberation War in 1971. In Bangladesh, 21 February is observed as Language Movement Day, a national holiday. The Shaheed Minar monument was constructed near Dhaka Medical College in memory of the movement and its martyrs.