For a K-8 environment, it might be worth looking into local e-waste recycling non-profits or university surplus programs. Often, large institutions rotate their hardware every 3-4 years, and they are usually happy to donate older but functional Chromebooks to schools in need. Also, check out 'DigitalEquity' initiatives in your area; they often have streamlined pipelines for this exact scenario

Local liquidation firms and those in nearby metros like Baltimore where the biotechs are might also be able to help. I’ve seen entire palettes of Chromebooks sell relatively cheap at auction. I doubt the liquidator will be able to do it for free but they can ask clients if they want to donate certain lots instead of auctioning them off or if you find a sponsor they might be able to notify you and give you first dibs when a lot shows up.