Wrong.
Much before Savitribai Phule, it was Hotee Vidyalankar.
Around the 1770s, Hoti Vidyalankar, a renowned philosopher from a kulin Brahmin family of Bengal, established her own chatuspathi (a traditional center of higher learning) in Kashi. Her school became a sanctuary, where women, particularly young widows, could access advanced scriptural education.
Hoti Vidyalankar was a scholar, philosopher, and educator, who ran a traditional Sanskrit institution. She was a profound authority on Sanskrit grammar, poetry, Smriti (law), mathematics, Navya-Nyaya (logic), and Ayurveda. Her profound erudition deeply impressed the pandits of Varanasi, who officially hounored her with the title ‘Vidyalankar.’
She taught advanced many subjects, which included intricate grammar commentaries, Hindu philosophy, and medicine.
You need to get over the fake of narrative Phule starting the first girls school in India!