Xiao Ming's calculation method is wrong. See explanation.

Analysis: This question examines the arithmetic average and the weighted average.

Solution: Last year, Xiaoying's family spent different amounts on food and education, so the growth rates of these three items were different, which had different effects on the growth rate of total expenditure. We should use weighted average instead of arithmetic average to calculate the growth rate of total expenditure.

.

So Xiao Ming's calculation method is wrong.