Happy to help here. In my experience grading BDR performance comes down to 4 key elements of their job;
Targeting
Which accounts is my bdr going after?
Which titles of people is my bdr going after?
Once you know that you can compare ok what % of their outreach are to ideal personas
Activity
Are they meeting the required output of activity on a day to day basis?
Usually this is measured in calls and emails sent
Measure % achievement of daily activity against their daily goals
Content
Are they using company recommended cadences or sequences?
Measure % of emails that follow the recommended sequence or cadence
Sales Accumen
How good are they on the phone?
Now this depends on your process. Normally with BDRs the objective is to schedule a follow up call with the sales rep. So to track this you would want to look at of the people they got on a phone how many did they get a next call with?
This is the framework I recommend to my clients. Happy to chat about it more or how specifically to set it up in Hubspot if you are interested.
Best,
Mike