When counting in ones, due to the repetition of the ‘teen’ sound, pupils can mistakenly say ‘twenteen’ instead of ‘twenty.’ The ‘ty’ in 20 must be reinforced and base 10 equipment can be used to show why 20 is not a teen number.

When we count in tens, the multiples from 20 to 90 all end in a ‘tee’ sound, which pupils may mistake for the ‘teen’ sound. This may result in them seeming to count correctly up to 90, but then saying 20 instead of 100. This indicates that whilst counting, they were actually thinking/saying ‘teen’ instead of ‘ty’.

When a pupil has a speech or hearing difficulty, these numbers will need even more targeted focus.