create record in another eneity using webresource.

I have Students and Tags 2 different Entities, 

Can I add records in Tags Entity while saving records in Student entity.
Can we create records in another entity using a webresource?

I have to use a WebResource not a workflow,
as we use:
Xrm.Page.data.entity.save();
it saves current entity record only.

is there a way thanks.