This is a great resource for self warm up and practice. Just as you wouldn't run a marathon before warming up, singing with good technique and long term health are directly affected by warm up and preparation of singing. These guides offer suggested warm pus that cater to mixing it up as well as covering the essential basics. Though these are not directly suitable for a classroom experience, I have found they are enjoyable for private voice students.
These are some related research and periodical articles that have come tom inform my teaching beliefs and practices in the classroom , especially those pertaining to music education