If you want your Recipients to sign the School Form:

If you've selected Recipient: User, and you want the User to sign the form, you'll add the "User Signature" block.

If you've selected Recipient: Parent of User, you'll want to add the "Parent Signature" block.

If you've selected Recipient: Both, you can add both the Parent Signature and User Signature block, if you want both users and their Parents to sign the form, or you can add one or the other. If you add the Parent Signature block, only the Parent will be required to sign the form. If you add only the User Signature block, only the User will be required  to sign the form.