The charts compare the school funding in 1981, 1991, and 2001 respectively.
According to the first pie chart, the largest portion of total school spending was teachers' salaries(40%) in 1981. This was followed by other workers' salaries, resources and furniture and equipment, which account for 28%,15% and 15% of the chart in particular.

In 2001, we can see that there were some changes in school funding if we compare with the data from 1981 and 1991. Expenditure on resources such as books had increased to 20% by 1991,whereas
salaries for other workers had been dropped.However,expenditure on salaries for teachers remains fixed.

Overall, It is seen that, school funding of resources and furniture and equipment shows remarkable changes, while the other categories shows stable trends over the period.

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Note: You can also do it this way.

1. Introduction- paraphrase the question

2. Overview- describe two main or general things

3. Details

4. Details

And it would have been better if I had seen the charts. I would be able to correct and add more things.