I have very mixed feelings about the idea of rats being great pets for children. Including in contexts where the parents have access to well-bred, pet-quality rats and are being as responsible as possible, supervising interactions with younger kids and making sure the cage stays clean if the kids lose interest or can't do it, etc.
Pet-quality rats are very sweet and docile creatures, affectionate, highly trainable, and can tolerate a lot of handling but don't necessarily require it.
If the child goes to school or daycare etc, rats should do just fine keeping each other company and/or sleeping while their human is away.
They don't need to be walked, or let outside multiple times a day/night.
The short lifespan means less of a commitment in terms of specifically duration than with something like a dog or cat.
You (in theory) get to decide how much access the rats will regularly have to any areas of your home beyond their cage.
Biting (imo) is never a non-zero risk. Sudden behavioral changes can come about in previously well-tempered rats due to things like pituitary tumors or hormonal aggression. And rat bites are powerful.
Pet-quality rats can tolerate a lot of handling, but not rough handling. They are tiny. They also have sharp little nails, which might scratch up a child even by accident, which in turn might cause the child to squeeze or drop the rat. Lots of potential for both sides to get hurt.
I cannot tell you the number of posts I have seen about someone's rats escaping from the cage, or during free-roam time, and disappearing into the house. The last post I saw about this specifically mentioned that a child let the rats out. This is an extremely dangerous situation for a rat.
Rats are not automatically a smaller financial commitment than other pets. They are very prone to health problems, and they're often more expensive to treat because they are so small and require a vet with exotics training. And you need at least two of them, ideally more. So you might spend the same amount of money (or more) in vet bills on a small group of rats over the course of 2-5 years as you would on a dog or cat over a much longer lifespan.
The health problems are also a thing the child will be subjected to repeatedly. Rats go downhill very fast. It can be quite dramatic and even traumatizing to experience, as the child in the worst-case scenario will not have time to adjust to the idea that their pet is very sick and might not pull through.
This is a cop-out, but I think it depends. It depends on the child(ren)—do they want rats? Would they be just as happy with some other pet? Are they able to understand the cons? Are they emotionally equipped for pets with such a short lifespan and so many health concerns? Can they be relied upon not to let the rats out of the cage unsupervised? Etc.
It depends on the parent(s)/guardian(s)—do you want rats? Are you emotionally equipped for pets with such a short lifespan and so many health concerns, and your child(ren)'s potential reactions to that? Can you afford to take multiple rats to the vet, potentially once a month or more? Are you comfortable handling rats if your children can't, to get them into a carrier, check them over periodically for lumps, etc?
It depends on the living situation—do you own, or rent? If you rent, what does your lease say about pets? Some specify cats/dogs only. Do you live near a vet who sees rats, and who isn't fully booked all the time? Are you planning to move within the next five years? How far? How will you transport the rats? What is the vet situation in the place you're moving to? Etc.