The letter group 'ch'  is sometimes used, for example chemist. chemical, chemotherapy etc. but this is an exception.

Other exceptions to this pattern are some brand names such as kit kat, and words taken from other languages/ cultures such as kangaroo.

Here are links to activities to help you explain and reinforce this pattern with your learner.

List of words - for word sorting activities. 

http://www.gdss.glasgow.sch.uk/Websites/SchSenRosepark/UserFiles/file/Spelling/Words%20to%20help%20explain%20spelling%20k%20at%20start.docx

Poster with visual clues to remember the patterns.

http://www.gdss.glasgow.sch.uk/Websites/SchSenRosepark/UserFiles/file/Spelling/k%20c%20kettle%20poster.pdf

Written text to use in highlighting and word sorting task.

http://www.gdss.glasgow.sch.uk/Websites/SchSenRosepark/UserFiles/file/Spelling/written%20task%20for%20sound%20k%20at%20start%20of%20word.docx

Movie showing word sorting and kite/ cat visual as a memory aid.