Peters edition
http://www.sheetmusicplus.com/title/Piano-Sonatas-49-Complete-in-5-Volumes-Volume-2/963283

Henle edition
http://www.sheetmusicplus.com/title/Joseph-Haydn-Complete-Piano-sonatas-volume-II/3764931

Which one is better for kids? Henle is 3 times more expensive, is it really that good?

Teacher lent us her Peters edition and it has "Urtext" on the cover, is peters edition considered as Urtext too?

For kids it probably does not matter. Cheaper may be better if they are going to get marked up.

The Vienna Urtext edition from Universal is also a respected edition.

The Alfred Masterwork edition is the most practical (most of the books in this series are). Maurice Hinson, I think, is the editor. Intelligent scholarship, though you may not agree with every dynamic marking. I generally save the urtext for upper level college performance majors.

Edition probably doesn't matter at this point. Just get the cheapest book and only the sonata(s) that you need. Really no point in getting the complete set of sonatas when you're playing one or two movements.

You might want to check the Peters Edition for font size, as Peters has a habit of squishing a zillion notes onto one page.

I have the Henle. It's pretty good, but I think Vienna Urtext is better for Haydn.

Of course it matters! Why would you start any child out with bad, cheap editions? I suppose, if they're just horsing around with the piano and it's nothing very serious to them, then sure, use whatever you want, but if the student is truly interested in learning (and I would think that's why they're taking lessons and the reason their parents are paying for them), then start them off with nothing but the best in every aspect of their musical/pianistic education.

If they are at the stage of playing Haydn sonatas, they are at a stage to have a good edition. My first choice is the Vienna Urtext, Henle second. I don't care for Peters.

+1

It's just a prejudice on my part, but I reserve Henle, UE, et al., for Bach, Schumann, Chopin, and use Alfred for the others. Hinson and Palmer have done a very good job of editing, they are easy to read, and as most students are not going on to be performance majors, Alfred works well for them.

Agreed. I use the Alfred/Hinson for myself, too.

I agree with the assessment of Alfred. What I like most is the extra information given with the music. It is very educational for the students, although as they become more experienced, it's not necessary and sometimes it can be a hindrance (I'm thinking mainly of Bach editions). I love Henle, especially now that I'm a bit older and can really appreciate reading clean scores .