What sized backpack for pre-school?

My DS starts pre-school in Feb & I'm trying to figure out what sized backpack to get him.

He doesn't need to take sheets, just m-tea, lunch, change of clothes & a hand towel. As his lunch will go straight in the fridge, I'm considering getting him a lunch bag that won't actually go in the backpack.

I've seen some backpacks sized about 25W x 29H x 10D. This isn't large I know, but do you really need a big bag? My son is a little man of 13kgs (3.3yrs).

I'm keen to hear from those lovely mums out there who have done this b4 :-)

Thanks

oh gosh....my son who is off to kinder in feb ( same thing?)..we got him a new one to also last for school....ill post a pic...but its not super big....i figure he will bring home alot of stuff and ill ensure a change of clothes et....

I brought the medium backpack from mooo for my DS, who is also starting preschool this year and the dimensions of the bag are very similar to the one you've got in your post. In the past for my other kids I've just used one of the character backpacks which would also be a similar size, but I wanted to get him something that could have his name put on it without using a bag tag or anything.

My DD has one about the same size. Last year we used a little WAHM satchel of similar proportion and rarely did it get used except to store her hat and occasionally her shoes lol
Anything they make they want to show you, so they will be carrying it, and school paintings are always huge so they don't go in there either.