I can’t believe I haven’t asked this question yet!
I only bothered to learn how to spell diarrhoea recently, and I teach English for a living. Haha.
Here is a list of words 12-year-olds in my country are expected to learn to spell:
Commonly Misspelled Words for Editing (Alphabetical Order)
Abundantly
Accelerate
Accomplish / Accomplished / Accomplishment
Accommodation
Accidentally
Accumulate / Accumulates
Achieve
Acquaintance
Announcement
Apparently
Appropriately
Argument
Atmosphere
Attended
Barbecue
Beckoning
Beverages
Believe
Beginning
Business
Camouflage
Challenge / Challenged / Challenges
Changeable
Chosen
Committee
Compliments
Competition
Congratulations
Consistent
Contagious
Crushed
Curiosity
Deadline
Delicious
Definitely
Description
Destruction
Devastation
Development
Different
Dialogue
Disappear
Disappointment
Dumbfounded
Ecstatic
Effective
Encourage
Enormously
Enthusiasm
Environment
Equipment
Explanation
Exhibition
Exceed
Experience
Extinction
Embarrass / Embarrassment
Fascinating
Favourite
Fluid
Forward
Government
Guarantee
Humorous
Immediately
Initially
Innovation / Innovative
Interpret
Interesting
Invited
Judgment
Knowledge
Lethargic
Leisure
Magnificent
Maintenance
Manoeuvre
Memento
Manner
Medicine
Mechanical
Mischievous
Nostalgic
Noticeable
Occasionally
Occurrence
Overwhelming
Parliament
Particular
Peculiar
Perseverance / Persevered
Pleasant
Popular / Popularity
Possible / Probably
Possession
Principal / Principle
Procrastination
Pronunciation
Quote
Receive
Recognition
Recommendation
Recuperate
Referred
Rejuvenate
Relevant
Reminisce
Respectively
Restaurant
Reunion
Requires
Rhythm
Schedule
Scissors
Scratching
Scrumptious
Separate
Sergeant
Several
Society
Souvenirs
Specially
Stationery / Stationary
Successful / Succeeded
Sustained
Sudden
Survive
Technique
Tomorrow
Topic
Truly
Unique
Until
Uphill
Useful
Vacation
Vacuum
Variety
Various
Venturing
Wasted
Worshipped