وَلَا يَجُوزُ لِلرِّجَالِ أَنْ يَقْتَدُوا بِامْرَأَةٍ أَوْ صَبِيٍّ.
Meaning: It is not valid for men to follow a woman or a boy in prayer.
This is the classical Hanafi rule regarding leadership of adult men. A woman leading women, or a minor leading other minors, is a different case and should not be collapsed into this ruling.