alt Hacker NewsLaptops can be useful: they can (and should) be locked down, and there’s lots of digital media that teaches effectively, probably even better than anything on paper.
(EDIT: Actually, probably not better than paper. I remember a study that note-taking by hand produced significantly better scores than typing; moreover, drawing is easier on paper, and some assignments are better drawn. But laptops can still be useful, and some assignments (like coding) are better digital. So ultimately, I think laptops should be incorporated alongside pen-and-paper.)
For 2) I agree with the general idea (“static” websites should never be slow), but the aforementioned digital media includes some that can run on low specs. Worst case, you can give students PDFs of physical assignments (with form elements to put answers); but I’m sure there are some minimal websites with K-5 material.
Laptops are NOT useful for any reason in a school classroom below the 9th grade or so. No, not even for test taking, educational videos, or interactive demos.
Maybe for computer science classes, but even there I'd prefer to use shared desktop computers.
There is a lot of research that shows that the depth of understanding the material directly depends on the amount of effort you put in. Or that actually writing down things by hand increases the amount of recall.
And to add to this, it looks like fine motor skills also directly influence brain development and may improve the IQ. The association of higher IQ with better fine motor skills is now well-established, but it also might work in reverse.