If you want to teach kids which letters to write first, start with the “tallest” letters. These letters are t,b,k,l,h. Get wide ruled line paper with broken lines in between the solid lines. Label the top line sky line, the broken line plane line, and the bottom line grass line. See the attached photo taken from Barbara Wilson’s Fundations website. http://www.fundations.com/
When practicing with your child refer to the lines as stated above, it gives them a reference point and a pattern to remember when writing these letters. Once your child masters these letters move to the rest of the letters in the alphabet which start on the plane line.