Planning is a future-oriented behavior. It intends to bridge effectively and rationally between present and future events, improve the future state and adaptation of an organization and produce meaningful results. However, when circumstances change, the tendency to stick to existing plans may prove ineffective (Mankins & Steele, 2006). Improvisation offers a flexible mode of operation which allows adaptation when conditions alter (Moorman & Miner, 1998). In this sense, improvisation is complementary to rational planning (Pentland & Feldman, 2008). In light of the growing uncertainty characterizing the environment in which organizations operate, organizations need to rapidly adapt themselves to changes while attempting to promote their effectiveness and relevancy. Improvisation is a spontaneous reaction based on previous knowledge, rational thinking and creativity, and therefore may provide an alternative mode of operation. It is important to note, however, that although improvisation involves tacit knowledge, spontaneity, creativity and intuition, it is still based a minimal structure (Cunha et al., 1999), implying that it is not a chaotic occurrence leading to anarchy but rather a controlled activity based on articulated knowledge. A minimal structure reflects the rules, norms and social identity of organizational members. While articulated knowledge is based on consistent and rational thinking that may be taught and transferred relatively easily, tacit knowledge is circumstantial, less systematic and is often used to cope with a given incident rather than anticipate future events. Individuals are constantly involved in a circular process (Hildreth & Kimble, 2002) during which they provide and receive information from others that is internalized and used to form their tacit knowledge (Nonaka von Krogh, 2009). Hence, improvisation offers a blend of declared and tacit knowledge.                                                           

Although public schools operate in a rather stable organizational environment as their continuity is guaranteed by the state regardless of the quality of their outcomes, their organizational environment is gradually changing to quasi-market circumstances, producing competition more than ever before (Nir, 2003). These circumstances require schools to introduce changes and adapt. Improvisation may contribute to schools' adaptability, relevancy and effectiveness, although so far its significance in the context of public schooling has not been empirically explored.  

The point of departure for the current study is that improvisation is likely to promote leaders' contribution to school effectiveness. This may be true in particular for transformational leaders who are committed to promote innovations, original modes of operation and creativity (Sosik, Kahai & Avolio, 1998). Transformational leaders emphasize creativity and constantly search new solutions for routine as well as unexpected problems. Therefore, it may be argued that transformational leaders who improvise are likely to promote the effectiveness of their school. It is important to note, however, that school leaders' tendency to improvise may also depend on their professional level, which is considered crucial when individuals are confronted with unfamiliar events and on their tolerance for ambiguity that determines their willingness to become involved in new endeavors involving risk and uncertainty (McLain, 2009).

Hence, the study explores the following research hypotheses:

1. Improvisation is a multi-dimensional construct and its dimensions described in the organizational literature will also be identified in the context of public schools.
2. A positive correlation will be found between transformational leadership and the tendency to improvise.
3. Professionalism and tolerance for ambiguity will predict principals' tendency to improvise.
4. Improvisation will mediate the contribution of transformational leadership to school effectiveness.

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