The subject of history of English

k’>tʃ cild (child) ceosan (choose) hwilc (which)

sk’ > ʃ sceal (shall) sceotan (shoot) sceort (short)

kg’ > dʒ brycʒ (bridge) hrycʒ (ridge) wecʒ (wedge)

Back ɣ sound before palatal consonants turned into j - ʒear (year).

So, the words that started with sc or j acquired a sibilant or j; if we find that a word still has g or sc/sk at the beginning there is a strong probability that it was borrowed from Scandinavian and replaced the Old English form (e.g. give, skin) or together with the old word formed a pair of etymological doublets (shatter/scatter, shirt/skirt). Some words of Greek origin (school, scheme etc) will also have sk.