Cast on 14.
Begin knitting sequence as follows:
Row one: knit two, purl two, knit 6, purl 2, knit two
Row 2: K 4, P 6, K 4
Repeat these two rows 5 more times, ending on a purl row
Next row: Knit 2, purl 2, slip next 3 stitches to a cable needle and place it in back, K3, K 3 from cable needle, purl 2, knit 2
Repeat row 2
Repeat this whole sequence until the knitted band fits around your head. Cast off, sew ends together neatly. Pick up stitches around the side of the band with a 12" circular needle. Aim for between 60 and 80 stitches (80 will make the hat slouchy-er)
Plain knit for about 4 inches. Divide the number of stitches by 5 (X), and knit one round as follows: knit (X) amount of stitches, place marker.
Knit to 2 stitches before each marker, knit 2 together and knit a round in between. If the hat looks too tall for your 5th grader, then simply eliminate the round of knitting in between.
Feel free to play with the cable knitting. See this site for a video on crossing cables. We use a very short double-pointed needle or an extra sock needle for the cables. See my own version of this pattern here.