Explanation:

- Option 1: Free accommodation provided to school principals

This is relevant. Providing free accommodation is a benefit-in-kind and a part of compensation of employees.

- Option 2: Free education of students whose parents work in schools

This is also relevant. It is considered a benefit provided to employees, so it’s counted in employee compensation.

- Option 3: Wages and salaries in cash

This is directly a part of compensation, so highly relevant.

- Option 4: Old-age pensions

Correct Answer. This is irrelevant in the estimation of compensation of employees, as pensions are transfer payments and not a part of regular employee compensation.