Creativity is a skill, a knowledge and an attitude. Some might say it is core to learning and should be taught as a discrete subject, others that it is domain-specific only, while others argue it already is taught through the creative arts. All such positions have some validity to some extent. 
Creativity can be developed or supressed in schools; the latter idea is pushed by Ken Robinson as one of the fundamental problems with current education systems across the world, so let’s bust some myths. 

What is Creativity?

Creativity is a learning attitude that requires knowledge. To be innovative with ideas and concepts there is a requirement to have some basic concepts and knowledge.
Creative thinking can be defined as the thinking that enables students to use their imagination to generate ideas, questions and hypotheses, experiment with alternatives and to evaluating their own and their peers’ ideas and final products. 
Key words here are:
As teachers in all subjects, we need to create opportunities for these processes to happen. By doing so we can encourage creative thinking to thrive.
Summative assessments are important to establish what knowledge is embedded in young minds, but along with this, formative assessment (reflective and ongoing) allows students to question and explore what they know - rather than just accept knowledge and facts as immutable and set.
If children are not asking questions, then there is a chance they are being passive receptors rather than active learners. 
Students must have a solid understanding of the basics of knowledges and skills in a subject if they are to then experiment and be creative. Creativity and foundational skills need to complement one another. 

Fostering Creativity

Allow students to make mistakes, view alternative possibilities and perspectives. Creativity will thrive if students feel confident in their foundational knowledge and see a value in it so that learning is based upon intrinsic values rather than extrinsic rewards.
Teachers’ need to value original thinking,  as well a ‘correct’ response. This includes instilling values such as seeing mistakes as learning opportunities. For neurons to fire intellectually in the classroom, students require both a supportive and challenging learning environment. 
Creativity is found across all subjects. Mathematics, for example, is highly creative. The purpose of mathematics is to solve problems, using previous formulas and knowledge to find new innovative solutions. That is creativity.
Science is similar – to find new understandings and solutions to the previous unknown. This requires the ability to make mistakes and learn from these. Even the ‘creative’ arts, while embedding experimentation and play at their heart, require a knowledge base first to then experiment and be creative with. 
Most subjects can adapt the techniques used in high quality ‘arts’ practice to enhance creativity in their own context. 
Of course, the highest level of creativity happens when both students and educators darw upon knowledge from across multiple subject areas and make  connections that create new understandings.
Curricular connections - a polymath approach to learning and communication between subjects,  where all knowledges are valued; rather than silos -  is perhaps the best hope for schools to foster true creativity.