I am an international UK born student currently in high school in Canada. Let me just start this off by saying my academics are very poor, and I am aware of that. My gpa is around 3.0-3.3 and I scored a 1650 on the SAT. I applied to Harvard because my parents told my to apply (honestly, I have no idea what they were thinking).
About 4 weeks prior to submitting my application to Harvard I was contacted by a Harvard Alumni who told me that he was asked by Harvard to interview me. I did the interview, but I am still very surprised. Why would Harvard interview me with such poor grades? Why even waste their time? Does this mean anything?
Oh I forgot. Some of my extracurricular activities include:
Track and Field
Ranked 5th fastest youth sprinter in Canada at the 2015 Canadian Youth Nationals
Hold a provincial sprint medley record
Recognized nominee and MVP for athlete of the year by my school and track club
Volunteering
Dedicated over 100 hours to my community by working in my church as a youth leader
YouTube
I run a YouTube channel with over 7,000 subscribers and almost a million views. I make videos that promote humour and well being to those around me. My videos have had a major impact on the lives of others.
Even with these extracurriculars, i’m sure grades come first for Harvard.
I am not sure how it works in the UK but the thing is that Harvard will try to assign as much interviews as possible for its applicants. In the international pool, due to limited alumni, they might only assign interviews for “pre-screened” applicants. However, I heard that there is a big alumni association in the UK so I suppose it worked similar to that of the US, meaning that interviews are given based on availability of interviewers in the region.
But I didn’t get my interview in the UK. I was born in the UK but i’m attending high school in Canada. I got my interview in Canada.
I don’t know, maybe you have something interesting or it could mean that they are giving you an interview opportunity like everyone else for equality of opportunity and meaning that they might not have “pre-screened” you. Anyway, if you didn’t want an interview, you could have sent an email to the alumnus interviewing you to thank him/her and politely decline so as to not waste your or his/her time.
P.S: Maybe your 5th place as a youth sprinter might have caught their eyes or something.
Oh its not like I didn’t want an interview. I greatly appreciated the opportunity and couldn’t believed that Harvard even considered me with my current grades. However, I do not want to get my hopes up. But yea as you said, perhaps something in my application stood out, or perhaps they’re trying to give me an equal opportunity like everyone else.
Thank you for your help
Sure, be happy. At least you got an interview unlike some others 
Just be content and finish your year strongly. No one has a chance at Harvard anyways.