So I basically emailed a professor at a local university and luckily had a chance to join his research team. Since this is an unofficial internship (my professor never had a high schooler or an intern at his lab team before) I wouldn't receive any certificate for doing it. My question is: how would colleges know that I actually did this?
Also, how long should I do this internship until it can be considered "meaningful" experience? Currently I'm spending about 30 hours per week at the lab, and I was initially planning to do this throughout summer break (so about 2 months), but I may do it for longer if I decide to ask my professor for a recommendation letter.
1) The best thing to do would be to ask the professor for a Rec Letter. If he mentions the internship/research (which he obviously will), the colleges will know that you did it.
2) Doing 30hours/week is actually A LOT. To give you some context, college seniors do 40hrs/week of research in summer as a full-time 'job'. So basically, the time you've put into this is impressive as an HS student!
3) Colleges rarely fact-check every part of your application so unless you think the research is a very essential part of your application, it's okay if you don't have any 'proof' of it. That being said, it's always better to include 'proof' through REC letters, School Transcripts, Certificates, etc.
To keep this community safe and supportive:
I agree with this ^^