To write English alphabet letters for elementary school students, it's important to introduce each letter with its name and sound. Here's a simple example:
A is for Apple. It sounds like /æ/.
C is for Cat. It sounds like /k/ or /s/ (when followed by 'h', as in 'ch').
D is for Dog. It sounds like /d/.
F is for Fish. It sounds like /f/.
G is for Giraffe. It sounds like /ɡ/.
H is for Hat. It sounds like /h/.