My two cents on value...
Here are a couple of value favorites that I use with middle schoolers --
maybe they can be adapted for HS ? I try to come up with short and sweet
value studies for kids that don't have much art time in their schedules, and
at this age, seem to want art to be more fun than work.
1) Popcorn Study (simple) -- students get a cup of popcorn and choose the
most interesting piece in terms of shape (they eat the rest, which they love
to do.) They then draw it, enlarged, on a page. First they use pencil, then
go over their design with a sharpie. They make a value scale using patterns
to represent five shades, light to dark. Next, they look carefully at the
popcorn and render each surface with the value pattern that corresponds to
what they see -- the drawings look interesting, like faceted jewels. This is
a fun intro to value scales and I find using high-contrast black/white
patterns adds to the assignment challenge. Decisions have to be made in order
to fill in the shapes. The irregular form of the popcorn provides structure
with wiggle room for inaccuracies, and the students feel successful with the
2) Crushed Coke -- Each student gets a piece of black and white paper to
free-cut into a high contrast shape collage. Next, they take a Coke can and
crumple it. They study the can and use the high contrast collage as a ground
for a drawing made with a variety of greyscale materials (charcoals, ebony
pencils, white chalks, etc.) The challenge is in making the can sit
comfortably in the foreground, with the high contrast collage receding to the
back. This brings together contour drawing and composition, and really tests
their understanding of value contrasts. The form of the can, part geometric
and part organic crumple, is a good challenge, too. The kids seemed to like
this assignment, too.
Good luck and thanks to all who are posting so many good ideas!