Is my teacher flirting with me or is he just friendly?

My teacher (M30something) asked me (F18) to go play tennis with him (adding "maybe it is better that we go after the end of the school year") and I agreed. A few days later he reminded me of this, so it seems like he is looking forward to it.
He is always very nice and affectionate to all students, but is this also considered being friendly or could it be considered flirting? I mean, it's not very common for a male teacher to ask a younger, female student to do something together just the two of them outside of school, is it?
But I don't know, maybe I'm reading too much into it and he just really wanted to go play tennis with someone lol.

P. s. He asked because he found out I play tennis, and he also enjoys this sport.

P. p. s. I wanted to underline the fact that he is very friendly and nice to students and people in general, so maybe it is just his way of being (even though I think I’m the only one he has invited to do something together outside school)
Is my teacher flirting with me or is he just friendly?
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