initial 

scr – scrape, scrub, scrap, screw, scroll, scream, scratch, scroll, script, screen, scrabble, scramble.

str – straight, stripe, straw, strap, strip, strong, strain, string, street, stream, streamer, strawberry

spr – sprain, sprinkler, sprinkles, spray, sprint, sprout, spring, spread.

spl – splash, splatter, splinter, split, splint, splotchy, splutter, splendid,

skw (squ) – square, squawk, squad, squid, squeal, squint, squirt, squeaky, squeeze, squash, squelch, squiggle, squirrel, squirm, squadron, squabble.