Your question doesn't quite make sense 🙂. I think you mean "a laptop or a tablet" (if distinguishing by size) or maybe you meant "a Windows device or an iOS device or a Chromebook" (if distinguishing by operating system).
An iPad is a tablet with an iOS operating system, but tablets with other operating systems are available
The answers depend on the school. Is it a state school or private? What age is your child?
If the school website says students have to take a device into school, then it makes sense to have a tablet or very small laptop, as it is easier to carry. If they don't, then a laptop with a bigger screen on their desk at home will be most comfortable. It's reasonably common for older students (post-16) to either have both or else have a very small, light laptop.
If younger, then a tiny number of state schools require you to buy a specific device, usually a Chromebook (as relatively cheap). Some schools issue devices. Most don't.
If the school has no specific policy, then it doesn't matter, so long as whatever you buy can run standard office software such as MS365 or Google Classroom.
Personally I would always buy a MS Windows device for home use, because I associate it with my world of work. Parents in creative industries may lean towards iOS devices for similar reasons.
The first time my boys had to take a device into school was in year 12. I got a cheap chromebook, which did the job, even though it could only really run cloud-based apps. I didn't want to buy something expensive in case it was lost or damaged.
When my eldest went to uni, he needed something more powerful, as well as transportable, so I got him an MS Surface.