For a while now I have been wondering whether learnt or learned was the correct spelling, so with true googlish (this is not in the dictionary, so is it acceptable to use?) enthusiasm I searched and found some interesting stuff. It seems both learnt and learned are alternative spellings of the past participle of the verb. British English uses the irregular learnt, while American English uses the regular form; learned.
Some other verbs of the type -ed & -t: burnt / burned, spelt / spelled, dreamt / dreamed, leapt / leaped, spilt / spilled.
There are verbs where the opposite is true such as dived (British) and dove (U.S.).
New Zealand English which was established by colonists during the 19th century, had it's strongest influences coming from southern England, Scottish English and Māori, according to Wikipedia.
Applying to Education: Although both forms are correct, perhaps we should be using the British variation. What do you think and teach?