I find the keeping students especially young ones motivated is a very difficult question in fact.
The teacher has to adapt to the feel of the class, the atmosphere, the spirit of the students, their moods, are they over actived? quite? sleepy? are all sorts of factors to consider and more. Will I achieve my goals today?
One has to keep students engaged during the lesson at all time that is the difficulty that most teachers face on a daily basis.the different activities created and proposed might reach this but often only a low percentage of the class will. Repeat of the same material is very useful as well with different approaches. However, another fact I find might stimulate the learners more is Curiosity specially with children. Engaging them in the activities to discover the answers by themselves in little groups or individualy. Of course at time guidance from the tutor is required. Nevertheless students may have the feeling that they have found the rules which will in fact motivate them more in learning further. Curiousity is a key factor to stimulate them to learn more and more with less efforts and easyly.
This is difficult aim at time to reach and demand a lot of continuous involvement on the part of the teacher working often overtime and not getting recognition for it which is more and more the way in today's society creating disatisfaction among the staff and concequently leaving the profession.
More and more demands are made on the teachers nowadays and we tend to forget that we are all humans and have good and bad days....and have a personal life outside working hours.