Missing Admin password on Used Macbook

Purchased a used Mac (can't afford a new one) for my grand daughter to use for Virtual classes at her Middle school. Its a Macbook (mid 2009) with EL Capitan 10.11.6.

The company (now closed) that donated it did not give us the admin password. We also cannot access the Recovery Mode. Have tried Command +R and Command+Alt+R and it keeps booting to the home screen.

How can we reset the Admin password or wipe and do a a fresh install of the OS?