My six year old has been taking guitar lessons in a small group of his age (3-4 kids, 5-7 year olds). The teacher is considered very good and is famous in my city. He has been working for many years with small children, and also himself is an accomplished musician.
Anyway he told me it's a good idea for me to buy my 6 year old son his first guitar. He suggested a full size (4/4) classical guitar of a good Spanish brand (around 300 euros new).
At the music store they told me, and also as I read on the internet, for such a small child smaller guitars are suggested, like 3/4 or even 2/4. However our teacher insists on a 4/4.
His reasoning is that he should learn the correct size from the beginning, and anyway more complicated notes that required bigger hands he will not play anyway the first years. When time comes for him to play chords that need bigger hands, then he will already have grown enough.
I've also seen another very little girl bring her 4/4 guitar to the lessons! Of course her mom carries it for her, but that's what she uses.
I'm trying to figure out what to do here... Any thoughts? Note that I would really like not to change the teacher, basically because my son likes him, and when starting out, the stress of going to a different teacher and seeing new faces might make him not want any lessons at all.
EDIT: Many people who answered here figured out that his teacher teaches classical guitar. Indeed, and his lessons are at a conservatory. I've seen him also accompany the kids on a piano and he teaches theory using coloring books.