I live in Egypt and have a daughter about to go to school. My question is does she have to go from the first years to a girls-only school. Please note that the vast majority of Islamic schools are mixed for primary years (until the age of 11-12) and then separated afterwards. I know that it is preferable but the options are already very limited.

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Dear inquirer! Know that the segregation between males and females at all levels (schools - work …) is not only preferable as stated in your question, but it is an unavoidable duty. Such a separation keeps temptation away and prevents the evils caused by the two sexes mingling.
So, it is better to avoid co-education even at the basic stage of education so that children are not brought up to become accustomed to a bad form of social life.
We advise you to enter your daughter to a school for girls and Allah will help you.
Allah Says (interpretation of meaning): {… And whosoever fears Allâh and keeps his duty to Him, He will make a way for him to get out (from every difficulty).} [65: 2].
Allah knows best.