If girls came out of high school with a sound hashkofa and a commitment to being tznius, maintaining gender separation and keeping away from unfiltered technology, we can say that the high school essentially did its job.
The reality, however, is that largely that isn’t the case. The girls as it is are thrown into the jaws of the yatzer hora after seminary, with the expectation of entering college and a workplace, often with standards that make them feel that “seminary is over, now it’s the real world, and in the real world, you can do X and wear Y and it’s totally normal”
If anything, they should make seminary far longer, and get rid of the mystique of having to go to eretz yisroel. It costs a ton, because parents pay far more than tuition and flights; seminar girls always need money for things.
Seminaries should be like part time yeshivos; first 2 years are a full day schedule, with no college. After that, they can have college courses in the seminary, or go to work, but there needs to be a commitment to spending 3 hours a day in a structured torah study framework. And not every girl can handle limud hatorah, so seminaries should offer spiritually inspirational activities and speeches, stories, mussar groups, etc… there’s literally no mitzvah for girls to learn, it’s a tool to get them to be strong in their frumkeit – but if the tool doesn’t work, then scrap it.