How can I use data from schools in my district to develop the SDP?

The development of any educational plan, whether at the level of the school or the state, follows these steps.

Identify the end result you want to see. What kind of participation, relationships, processes, and higher order learning outcomes do you wish to find in your school, perhaps a few years from now? That is your vision.
Against this, assess where you are currently.
Keeping in mind the long-term goal, consider the appropriate strategies you wish to adopt to bring those changes about. Which activities will these strategies involve?
From your strategies, processes, and activities, select those that you want to complete in the coming year, and put them in a sequence. You will not have the resources to implement everything you want. So, select the activities you want to implement in the coming year. Now, for these activities, identify the duration, the start and end point, the people and the costs involved.

Putting this together gives you your plan. You will need to follow your state’s format for this purpose.

As you can see, in each of these steps, you need to use data.

While the vision should be qualitative in nature (written in descriptive sentences rather than figures), there are some aspects that will involve numbers. (You can identify which those are.)
Your current status, or the starting point of your plan, too has to be based on current data. You also need to go through evidence - that is, look at what worked well and what did not work well over the last year or two.
Data from previous years can tell you many things relevant for this year: what resources were available, what they were used for and if they were enough or too much; do you have experienced resource persons and materials that can be used this year? What more will be needed, and what further input will they need? If there has been assessment of any inputs earlier, what does it show for what you have to do this year?

On strategies and activities

A strategy is an approach or a broader objective, which requires many smaller steps (or activities) to implement it. E.g. your strategy could be: ‘motivate teachers’ - and the activities would be: to create benchmarks, implement observation-based assessment, hold meetings with teachers to provide feedback, and organise community functions to recognise good performance of teachers.

Similarly, your strategy could be: provide on-site professional development inputs to improve teacher performance. The activities involved would be: use performance standards and indicators to assess current performance, assess needs through performance assessment and interaction with teachers, ask for BRC to arrange for workshop for teachers, observe and support teachers in real time in the the class, collect and share videos of good practices, organise peer-sharing meetings, and so on.

You will need many different kinds of data to know if these strategies and activities work. These could be: findings of teacher observation, attendance of teachers in related events, teacher response, shift in teacher performance, etc.

Read this: How can I use SDP for developing the State Annual Work Plan and Budget (AWPB)? to learn more about how to use SDP for AWPB.