For those of us who teach very young children, who are still at the nursery or reception class stage (in Spain until 6 years), it can be very frustrating to see that after all our efforts, the children only remember a few individual words. I have been teaching at a nusery school twice a week for many years, I only see them for half an hour at a time, and only a few of those children actually go home at the end of the year with more than a few words learnt. This is due to the extremely little exposure they get to English, an hour a week is not enough, they would ideally need to be practising and reviewing the new vocabulary throughout the rest of the week in order for me to teach them something new each lesson. As this is not the case, since English is just an "extra" and not actually part of the syllabus, it is disappointing, especially for the parents who think that their child is going to come out speaking English, that they cannot remember the color orange when they go home after 6 months of English lessons.
However, if you have more contact with the children, you can get much better results by teaching "chunks". By chunks, I mean expressions or short sentences, instead of individual words. I have a class of five-year-olds in my language school, whom I see for two hours a week, and recently we have been learning to use can for ability. Children of this age evidently have no understanding of grammatical concepts, but you can ask them in L1 if they can do certain things, like swim or skate, and then go on to teach the English way of saying it. You can also teach through mime. Children love it when the teacher acts a bit silly, I have had many laughs when pretending to ride a bike and then falling off to elicit "I can't ride a bike" and this helps them to remember. The important thing is to teach them "I can ride a bike", instead of just ride, or bike. I actually taught the vocabulary first, and later added "I can" and "I can't". In our course book, the current unit includes the vocabulary: skip, slide, ride a bike, fly, play football, swim and dive. There are flashcards with the characters doing these activities, so in the second lesson, I used "Anna can skip", "Lee can play football" etc. Some of the brighter children started to use these chunks even in that very lesson! In a subsequent lesson, I introduced: "I can swim. Can you swim?" and encouraged them to reply "Yes, I can" or No, I can't". We had already practised hearing the difference between can and can't in one of the previous lessons.
What I would like to point out with these examples is that it is much more rewarding for the child and the teacher if the child has learnt a "chunk" of language, rather than just an individual word. I encourage the children by telling them that they can now say complete sentences in English! The child feels that they have learnt something important, and the teacher sees that the child is using real English, they are actually communicating, not just looking at a flashcard and saying what they see. I think this is especially important for 5 and 6 year olds because they are competent in their own language and if they can communicate in another language, they feel (and rightly so) proud of themselves, and want to learn more. It is much more motivating to learn how to really communicate something in another language, than just to learn individual words. I still remember quite a few words in German from school, but I cannot say a single sentence, and I therefore feel that I know no German. Our learners must feel the same, whatever their age.
Every year, at the beginning of term, I teach the chunks: Can I have a pencil/rubber/ruler/sharpener, please? along with Can I go to the toilet, please? as I feel it is much more positive for the children to ask for things properly, instead of saying "rubber please", and they do actually learn to do so. It is important to start these habits early on, and not let them off because they are so young. The more you can get a child to communicate, the better!