I don’t think that is the case (especially for a security conscious district), at least not at the current prices.
At my prior highschool (currently a college student so that was a couple years ago) the Chromebook model they used was ~$160 USD on Amazon. Of course there has been a bit of inflation since then (but they may have also been getting bulk discounts) so let’s call it $180. Some of those lasted 5 years, some got replaced in their 2nd year due to students destroying them. Let’s call it 3 years. $180÷3 = $60/year.
The CPU in the Framework Laptop 12 likely has 5 years of security updates from the release of the laptop (Intel CPUs get ~7 years from release but Framework used a 2 year old CPU to save money). If school districts care about having up to date security updates (which admittedly most probably don’t, but perhaps they should) that means upgrading the mainboard every 5 years. Currently the cheapest Framework Laptop 12 mainboard is $300 USD. $300÷5 = $60/year.
So the Framework Laptop 12 is an average of $60/year for just the baseline mainboard upgrades required to continue receiving security updates. Whereas dirt cheap Chromebooks are all-in around that amount including the costs of replacements for other reasons (such as the major one of students destroying laptops).
Edit to add: I do absolutely believe the Framework Laptop 12 is a better experience for the users and better for the environment that a super cheap Chromebook. I’m just disputing that cost aspect.