With Universal pre-k the state of New York is paying for all students provided that there is limited religious instruction .
If the yeshivas don’t hire the seminary girls they will be hired by the universal pre-k providers. Who will the parent want a middle aged tired teacher who can’t keep up with the toddlers or the teenage teacher who is full of vim & vigor. Some of these pre-k may decide to start a first grade and then a second and since they are the only ones hiring the seminary girls the yeshivas can’t compete and before you know it what started as a pre-k is a full fledged yeshiva.
Supply and demand dictates that the fewer applicants the higher the salary. Likewise once a larger number of girls go into different fields such as programming, medical billing etc… it will open new fields for the middle aged woman and there will be fewer candidates for these morah jobs.