Spelling rule
Teach final-consonant doubling with real contrasts.
The rule is useful when the condition is visible: one short vowel, one final consonant, then a vowel-starting ending.
Start with the base word
In hop + ing, hop has one short vowel followed by one final consonant. Double the p before adding -ing: hopping. The doubled letter keeps the o short.
Use the contrast that explains the decision
Hope + ing becomes hoping, not hoppping. Hope already has a silent e, so it is a different base pattern. Putting hopping and hoping side by side helps a child see why the extra p belongs in one and not the other.
Know the boundary
The condition matters. Rain becomes raining because it does not end with one short vowel followed by one consonant. Jump becomes jumping because its ending pattern is different. The point is not to double every final consonant before -ing.