Kids Piano Brands
Kids piano brands vary widely.
At the bottom are "toy pianos," which are pianos in name only: they have no strings but make sound with small metal plates. Toy pianos thus sound more like xylophones than pianos. But it is a good place to start if you want "cute." For this reason, expect it to last a year or two, perhaps, and then your child will move on to a real instrument. The largest, most well-known maker of these toy pianos is Schoenhut. They have toy pianos from $40 to $500.
Roland, Casio, Yamaha
The next step up are many brands of electronic keyboard. You can choose either a simple 48 key model, or an expensive 88 key behemoth with a host of features you will never use.
My advice, if you are a beginner or in charge of a beginner's musical education, is to get the simplest, cheapest model that has at least 48 keys, and whose keys are the standard 3/4 inch width. It seems like they sell for $79 to $99, Avoid the $29 to $59 price range, for they are often disappointing to the child. Later you can try a more complex instrument, if the child shows interest.
The three manufacturers, Roland, Yamaha and Casio all make decent entry level keyboards. Do not allow a salesperson to upsell you beyond $100. Stay simple.
Uprights: Kawai, Yamaha, Baldwin
I know people who have been given old pianos, sitting in a cold garage, and then they put them in a house to see if the kids will play it. This is a frequent scenario when you are getting a low cost, or even free, old acoustic piano. At a piano dealer, you will see these "junkers" marked up to $1000 and beyond. In reality, they are worth nothing.
But here is the downside. Acoustic pianos that are old and neglected are notoriously difficult if not impossible to tune and repair. Because of this neglect, there will be sticking notes or notes that don't play at all.
The other option is to try to get a decent Oriental piano, since most piano in stores are Chinese or Korean in origin. Examples are Kawai, Yamaha or Baldwin. They cost about $3500 (and up) and let the buyer beware, so here is the downside: Unless you are a knowledgable buyer dealing with the finest of dealers, it is 99% sure that the piano you are looking at ($3500 and up) is what is called a "second." This means that, upon manufacture, a tester has graded the piano and deems this piano "not of the first rank." It's new, for sure, but there are always various problems, undetectable to the untrained eye, that will eventually cause difficulties.
For this reason, be very careful if you plan to buy from a piano store. There are whole piano stores based on these "seconds" and it is the most common fakery that first time buyers face. The piano may sound and look good to you, but to an expert it may have almost no value.
Top Of The Line: Steinway
Be very careful. Just because it is a Steinway doesn't mean ANYTHING. It could be in such horrible, unreparable shape that no one wants it and it is a piece of junk that will cost you $200-$500 just to haul to the dump. That said, many of the finest pianos I've played have been Steinways, but they were maintained and tuned like a race car. Newer Steinways, I'm sad to say, are not as good. After about 1926 their quality started slipping away.
I've played brand new (2018) right out of the factory 9 foot Concert Grands in stores that were horrible, and sold for $125,000. If you're not an expert, get an expert. You should be able to get a quality upright piano for around $8000. But it all depends on the dealer: I've seen them offer rebuilt junk for $15,000 and up, with a grand old piano name like Chickering, Knabe or many other once-great brands.
Watch out. Piano dealers are desperate and many are failing. Many people give pianos away, since they are so expensive to move or get rid of. Landfills are full of old uprights. With luck, maybe you can catch a good one in time.