How many words?

Yesterday I watch two episodes of Steve Smith's series of videos about second language teaching.  (Have you watched them?  You should!)  I watched the two about vocabulary.  For Key Stage 3 and Key Stage 4 learners, Steve recommends introducing 10-15 lexical items in one go.  These lexical items may be single words, but they could also be short sentences or other chunks of text.

When introducing new lexical items, I've always kept to the maxim "the magic number 7 plus or minus 2".  Generally speaking, primary learners are in the "minus 2" bracket, and I consider 5 or 6 words to be a good number to introduce to them at once.  With the list of 11 main colours, for example, I split them into a group of 6 and a group of 5 and introduce and practise the two groups separately.  If the words or phrases comprise a considerable number of cognates, it's possible to introduce more than 6.

It's occurred to me that this significant difference between expectations in Key Stage 2 and Key Stage 3 could create difficulties for Year 6 children going into Year 7 and what they are used to.

What do you think?