Situational leadership classifies leadership into four styles:

• S1 - high directive-low supportive
• S2 - high directive-high supportive
• S3 - low directive-high supportive
• S4 - low directive-low supportive.

Hersey and Blanchard argue that a leader's style, whether participating, delegating, selling or telling varies according to the degree of a subordinate's ability and willingness to undertake the task in hand (McCaffery, 2004, p.64). The situational leadership (SLII) model describes how each of the four leadership styles applies to subordinates who work at different levels of development:

• D1 - low in competence and high in commitment
• D2 - moderately competent and low in commitment
• D3 - moderately competent but lacking commitment
• D4 - great deal of competence and a high degree of commitment.

To achieve the effective leadership the leader should diagnose the development level of subordinates in a task situation and exhibit the prescribed leadership style that matches that situation (Northouse, 2007, p.110).

You can find the model and a description at the page.