Choir vocal warm-up exercises

Because most of the exercises designed for older students are more suitable for one-on-one instruction, I decided that at the very end of the textbook there should be a series of voice exercises which can be used for group or choir vocal warm-ups. I anticipated that most of the people interested in the textbook will be choirmasters and teachers in schools, who for the most part work with groups of children. The knowledge acquired from studying this textbook should help them understand their students' vocal abilities and needs as well as the possibilities of one-on-one vocal practice (for example with solo singers or children with voice problems).
Even though an individual approach is somewhat limited when working with a choir, the responsibility of a good teacher is to provide the children with at least a basic voice education. For this reason, a group singing warm-up should be a part of each singing session. It not only helps to instil the most basic singing habits, but it also warms up the singing apparatus before the required performance.
The fifteen following exercises comprise a possible general warm-up exercise set, which could become a good "springboard" for beginner choirmasters and teachers. When working with a larger number of children you always have to base your work on the group average (age, talent, singing experience of the children). In individual voice training you can base your work on the current needs of the child (for example build the exercises around the vowel which the child manages the best and then apply the knowledge to the rest). When practicing with a choir or a in a group setting you have to adjust the exercises to the needs of the majority. Therefore, the following exercise set is assembled according to the usual choir needs and skills in order to be suitable for as many children as possible. If some of the exercises are not suitable to your needs, you can naturally skip or replace them with other exercises included in the textbook or some of your own.

Note:
You may practice all of the following voice exercises in both directions, i.e. ascending for warming up higher voices and then descending for lower voices.
I need not emphasise that it is not a good idea to force children to sing at the very edge of their vocal range. During warm-up singing in the ascending direction, altos gradually stop singing and likewise when singing in the descending direction, sopranos gradually stop singing.