Can I copy a DVD made by a high school to another DVD?

Yes. See

Duplicate a CD or DVD

1. Insert the DVD/CD;

2. Open Disk Utility, and select the DVD/CD from the left side list (select

the DVD/CD icon on top);

3. from the DU File menu select New | Disk Image from Disk 1;

4. Choose to format the disk image as DVD/CD Master, name the disk

image and click Save;

5. When the .cdr file is finished select it with mouse and press

COMMAND-I to open the Get Info and check the box to lock the file;

6. Choose the .cdr file from the left side list, click Burn, and insert a new,

blank DVD or CD.