Hi,
 
My son just finished first grade and he had a lot of "number sentence" assignments.  In his class, a "number sentence" was an equation (2 + 4 = 6).  Most often they would have to read a story and write a "number sentence" about it.  ("Two ducks were floating in a pond.  Four geese were in the pond too.  How many birds were in the pond?"  and he would then have to write 2 + 4 = 6)

Hi dblga, a number sentence is usually used when trying to figure out a word problem. For example, “There are seven cookies, but then Steve eats three cookies, how many cookies are left?” So the student will have to write out “ 7-3=4” Other times the student may just be given numbers and they have to create number sentences from them. For example, “The numbers are 2,4,6,” the child will then create number sentences “( 2+4=6),( 4+2=6),( 6-2=4),( 6-4=2)” I have provided a link below for a number sentence game for additional practice in learning number sentences, I hope this helps!