I agree! You are absolutely right. It is fine to use 'have' as a dynamic verb in this sense to mean "participating in", and it is correct to use the continuous aspect to answer a question about what you were doing at a particular time. "I was having basketball practice" is the right response.

Hmm, interesting. I agree with you and Su.Ki that there is logic to "I was having" in a case like this. But I still would advise you *not* to say that. :D Let me throw out a few alternatives with commentary. "Between 5 and 6 o'clock yesterday I was having 'Basketball Practice'". Here "Basketball Practice" is some kind of formal name for the lesson or event. That is technically correct, but sounds a bit second-language to me. "Between 5 and 6 o'clock tomorrow I will be having 'Basketball Practice'". Same comment as above. "Between 5 and 6 o'clock yesterday I had 'Basketball Practice'". That sounds better. "Had" means "I had it on my schedule". "Between 5 and 6 o'clock tomorrow I have 'Basketball Practice'". Same comment as above. "Between 5 and 6 o'clock tomorrow I will have 'Basketball Practice'". Mmm, starting to sound a little second-language-y again. "At 5 o'clock yesterday I was having basketball practice". Note that 'basketball practice' is not the formal name of anything. To me, this sounds very unnatural. Pairing the verb "to practice" with "to have" sounds very wrong to me. As I said above, it's ok to "have" <the name of some lesson> on your schedule. So you can "have Practice" (note the case) but you don't "have practice" (note the case). Also, it sounds weird to "be having" for an instantaneous point in time (at 5 o'clock). "At 5 o'clock yesterday I had basketball practice". A little better but still have the problem of "having practice", which tbh no-one will likely care about because they'll hear or read that as "having Practice". "At 5 o'clock yesterday I had basketball practice". This sounds natural to me. This will be interpreted as "my basketball practice lesson/session began at 5 o'clock yesterday".

thanks again, Caleb. I am more interested in finding out more about 'Natural English' than in rules. I can find the rules in my numerous Grammar books and on the Internet myself, but I am keen on sounding 'more English' though and avoid 'second-language impression'. Thank you!

I just want to quickly add that this is a very common use of had when talking about time or things that have happened. e.g. "The band had been playing all day" e.g. "The soccer team had a good season this year" or even "I had to use the rest rooms"

I think Su.Ki might be agreeing with your logic rather than answering the question as to how a native speaker would say it. Sometimes as a native speaker you don't know what something is that way that it is because it's just something you have always done. As such when presented with hard logical rules it's easy to agree with the logic instead of go with what comes natural. I can say as a native English speaker that most people will say "I had basketball practice". I don't know if there is a hard logical rule as to why this is the way that it is or if we are all just breaking the rules for the sake of sounding natural but if there is a rule, then I suspect that it's due to an event not being an object and therefore nobody can have direct ownership of it. You could run or manage the event, but that's different. Or maybe it's the way that we own our time and this is how we spent the time that we own. I didn't post this as an answer because I don't know the hard rule why. Just that it's what comes natural.