How do grade students with 100 % AI generated essays

I am struggling with an ongoing issue. My schools requires that at least one assignment be an essay. Starting in 2024, students have been increasingly using AI to write their papers. Sometimes 100% AI generated. I use multiple AI detection tools to verify. I have also instructed my students to write in Google Doc to produce a version history. But nobody did and the Google Docs they sent me are just essays copied and pasted from Word, so it is meaningless. I want to remove the essay requirement but the school requires it to indicate students can write and research and of course there objectives are undermined by AI. I also work with largely international students so there is the additional cultural barrier that I face. The course also requires discussion posts which of course are AI generated. How do we even assess students when everyone is perfect with AI? These course assessments are of course designed for a different time but I feel like the school is falling behind. Ironically, the school is pushing generative AI to all its faculty, but question is if the professors are using AI, what stops students from using AI

Look forward to your comments.