If I were to give my kids two NON hyphenated last names, where would they be in roll call at school ?

Unless you want to create more problems for your children later on in life, you may want to use the hyphenated version. The first last name would be used. If the last name was Smith-Jones, Smith would be used.

Non hyphenated names it would be the 2nd one they would use. If hyphenated they would use the first one.

A non-hyphenated last name would be read alphabetically based on the first of the two surnames. So, Baker Williams would be read in the order of Baker, not Williams.

probably the first one you give thern

I am surprised you can do that at all. Where I come from, the child takes the last name of the parents.

Most people would assume that without the hyphen, the first last name was actually the middle name and use the second last name for the alphabetical line-up.

If the name started with AAA, first; if it started with ZZZ, last.