The "Learning by Copying" debate has gone on for generations in art education, and is unlikely to be resolved any day soon. My take on the situation is this: In the secondary schools, where studio classes prevail, there are the practical considerations of time, materials and access to ideas to confront. If you have experienced a reduction of contact time with your students, their opportunities to draw and paint from direct observation is likely compromised. Using reference photos or copying master works is an acceptable, albeit not perfect, substitute for direct observation art activities. In addition, keep in mind these are students, not professional artists. Studio classes should teach, in addition to the creative process, art skills-- something that universities sometimes forget in their fine art classes. One of those skills is increasing the student's ability to observe all of the visual clues a given subject presents, and the use of photos can
provide that type of information.
Keen observation skills are essential to the technical side of art--perspective, color mixing, brush techniques, use of shadow, etc. Very often, the fine artists among us would rather not deal with that aspect of the creative process, but ignoring it can be at your own and your student's peril. How your students deal with those skills is part of what makes them unique and creative, which you nurture as much as possible. However, if your kids don't know how to hold a brush, it is pretty difficult to paint effectively, and if you can't effectively perceive the world around you, it's equally as hard to interpret that world through art.