User Access Rights getting cleared in Odoo 8

I'm trying to lea Odoo and developing a module. For the same, I just created 2 new user groups. ie. Parent and Faculty. I used the following code,

<record id="group_parent" model="res.groups">
    <field name="name">Parent</field>
</record>
<record id="group_faculty" model="res.groups">
    <field name="name">Faculty</field>
</record>

It worked fine and I can see these groups under the Access Rights tab in user's form view.

Then I was able to assign Faculty option for a user. But when I upgrade my module, it's getting reset the user's access rights.

After upgrading my module, how it looks like is:

It will be appreciable, if anyone can tell me the reason for this issue.