For each letter, make a unique symbol or shape or another letter or number. Make copies of this and have boys write a coded message for the boy on his right to decode

A	B	C
D	E	F
G	H	I
J	K	L
M	N	O
P	Q	R
S	T	U
V	W	X
Y	Z	1
2	3	4
5	6	7
8	9	0