Midpoint of a segmentPoints in the first quadrant
Find the midpoint of each segment.
The point halfway between two others is nothing more than the average of their coordinates — the middle x, the middle y. These free printable worksheets plot the two points and the segment joining them, and ask for the one exactly between.
If they get stuck

The answer key prints on a separate page.
The figure is the same one the distance sheets draw — two points and the line between them — because the picture a child reads is the same. What changes is the question: distance asks how far apart the points are, this asks what sits exactly between them. Reading the coordinates off the grid and averaging is the whole method, and it needs no formula to memorize.
The two coordinates are averaged one at a time, and doing them separately is what stops a child from swapping them. The midpoint of (−5, 1) and (−1, −5) is found by halving −6 to get −3, then halving −4 to get −2 — never by mixing an x with a y. Every step-by-step walk here does the x's on their own line and the y's on the next.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Midpoint of a segment, step by step