It appears from the pattern picture that the inversion of the pleats is actually done in purl. If so then the natural characteristic of the ribbing effect created with knitting say 8-10 sts then purling 2-4 will make it look pleated.
If you're doing true pleats with one thickness over another and the 3rd thickness toward the next pleat like in sewing, your knitted piece will be extremely thick and not likely to stay crisp except at the point they are stayed with a band or seam.
Another option is to use a liquid starch, mixing with water... for a light starching - 1 cup starch to 4 cups water and a medium starching - 2 cups water to 5 cups water. However, using starch, you'll have to do this each time you wash the acrylic or blend.
And another option is to permanently tack the pleat fold vertically from top to bottom after the skirt is complete. Use an embroidery thread and literally do a running stitch, making sure you aren't pulling too tight and be careful not to run the stitch to loose.
Pleated skirts are a classic style and I don't blame you for wanting them for uniforms. Done correctly and with lots of patience they'll be great.
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