Most kids who quit guitar quit because the guitar didn't fit them.

Wrong size, wrong type, wrong vibe.

Let's fix that in about 3 minutes.

TL;DR

1. Size first — match to height, not age
2. Acoustic for casual starters, electric for kids with a clear passion
3. Budget $150–$300 for something that actually holds tune and feels good to play

Step 1: Get the Right Size

Age charts don't tell the whole story. Use height instead.

A good rule of thumb: the guitar should reach roughly to your child's belly button when standing. If it's bigger, they'll struggle and get frustrated fast.

But in general:

Age	Size	Best for
4–6	1/4	Real beginners, tiny hands
6–8	1/2	Early elementary
8–12	3/4	The sweet spot for most kids
12-13+	Full	Teens with bigger hands

Here is a quick fit test at the store:

1. Have them hold it in playing position. 
2. Can they reach the first fret without straightening their elbow?
3. Is the shoulder relaxed?
4. Good if the above check. If not, go smaller.

Here are more details on getting the right sized guitar for kids.

Step 2: Acoustic or Electric?

This is a topic on it's own, here are the details on whether to get an acoustic or electruic guitar for a kid.

But in general:

My top pick: Yamaha JR1 (~$179). Solid, reliable, great for the price.

Here are the 3 acoustic guitars I can recommend.

My top pick: Squier Mini Strat starter bundle (~$250–289, comes with amp and cable).

I had a 13-year-old student whose parents held firm on acoustic because they thought it was "the right way to start." He barely touched it. They switched to electric, and suddenly he was practicing two hours a day. 

Remember this:

The best guitar is the one your kid actually wants to pick up.

What to avoid

• Full-size guitars for young kids. They're not going to "grow into it," they're going to quit.
• Cheap no-name brands under $50. They go out of tune constantly, which is discouraging and hard to learn on.
  Here are my thought on how much to spend on a kids guitar when starting out.
• Classical nylon-string guitars, unless your child specifically wants to play classical. They limit the music styles available and most kids find them boring.

And of course, getting the guitar is one thing, learning to play it is another. Here is a comparison of how much kids guitar lessons cost in person vs online.