iPad or Chromebook, it is a loose-loose situation for the next generation.
You are training kids to use expensive device with a walled ecosystem or you are training kids to use subsidised device with in practice walled ecosystem and with a questionable privacy policy.
The future generation will have it even worse than generation who grew up with Microsoft.
Other environments don't have the ease of administration that chrome os and apple devices have. If a device is stolen, you can lock it down. The settings are automatically pushed to the device, so kids and teachers don't need to fumble with trying to figure out how to print to the classroom printer. Because it's using google apps, sharing documents is built-in, so kids don't need easily-lost thumbdrives, and don't have the frustration of losing homework due to computer problems. Finally, it's relatively inexpensive. You can get a chromebook for $150, which is a lot easier on the budget if a kid accidentally breaks their laptop.
If you want to give another option, you need to bring something to the table that's as easy to use, as easy to administer, as easy to share content, and as inexpensive. Until you can bring those things, then all you have is an inferior product for the average teacher.
We permit any kind of laptop so long as it has a "modern" browser. I've got a few kids running Ubuntu or some other form of Linux on their PC laptops. We don't discriminate if they want to use something more complex; that said, the market speaks for itself. For early middle school, almost all parents choose the simplest option, the Chromebook.
You are training kids to use expensive device with a walled ecosystem or you are training kids to use subsidised device with in practice walled ecosystem and with a questionable privacy policy.
The future generation will have it even worse than generation who grew up with Microsoft.