English song lyrics from a gentler era... "Beauty's But an Idle Boast" is a little-known singing round that is very beautiful.
In the key of Am (shown), this round has a comfortable range... from Middle C to high C, fine for children and also women who haven't done much singing for years! However, the melody is more complex than beginner rounds such as Ah Poor Bird and Heigh Ho:
Because this is a complicated melody, I've also made this song available with Alphanotes - made-easy notes that make it possible for singers who are just learning musical notes to gain accuracy with this melody. I have a singer with a lot of ability, but not the skill to EASILY read a tune with multiple skips and a few accidentals and ledger line notes, and this easy-reader note version helped her to learn this song quickly (since I could not find a video online).
I neglected to put "1", "2", and "3" where the new voices are to begin, but I'm sure you'll figure that out! Each line of the music is one section, then at the next line, a new voice enters back at the beginning of the song...
Try the chords on piano or guitar as the group sings. With this particular singing round, I have found that it is easier to keep the singers on their notes by using the chords than by banging out the melody.
Don't let your voice students drop the breath in the middle of the lines - look at the phrase markings in the first arrangement above (not the lettered notes version). If they stop to take a breath after "but", and "to-day" in lines 1, 2, and 3, all the energy drops out of the line, and the harmony as well! Demonstrate this for your beginners - they will get it.
Make them carry the sound through to the end of each line. They can do all the breathing exercises for singing you want at the beginning of their lessons, but if they don't learn to apply it to real music, you are failing in your job. Make them HEAR themselves.