KS3 - Chocolate Challenge Observational Drawing Assessment

How do you get KS3 students to draw in controlled conditions for 80 minutes? ...Involve chocolate.
This is an ideal observational drawing assessment for KS3 students using pencil and colouring pencil, with the focus on proportion and tone. The resource can be used as a powerpoint for the assessment lesson, including: a hook/ starter question based on willpower; objectives; a clear outline of controlled conditions and four 20 minute drawing tasks. The first task is for students to draw the chocolate bar, wrapped, using tone with pencil. The second asks them to draw the chocolate bar unwrapped using tone. The third allows the students to take a bite of their chocolate and draw the bar using tone with colouring pencil and the final task allows them to eat the chocolate bar and draw the wrapper, again using tone with colouring pencil.
The resource includes a ten minute self assessment and four printable step by step sheets which break down the drawing process for less able students. Each task includes differentiated learning outcomes. Marking stickers are also included on word documents separately which correspond to the learning outcomes and make marking and standardising large groups of KS3 a lot more manageable.
All you need to do is get in the fun size chocolate bars.
N.B. If you have many Muslim students this is not a good lesson to do during Ramadan.