So for Lavender. Jack was a couple years older than her but he did go to Aurelius. I'm sure they are probably at least aware of each other, if not friendly! They will have lots to discuss now, though. Especially with the giant clusterfuck of wizard reveals recently. lol.
I can offer up Jillian Reed as a friend? She's a couple years younger than Lavender, but I feel like they'd get along really well.
Sam and Ana are both quite a bit older, but are both marginally friendly.
And for Francis, I can also offer Jillian's friendship. lol. She's also gay, and has tried to organize a few LGBTQ activities and such in town. So he'd have been welcome to come to any of those. Jack is super friendly, but I don't know that they have a ton in common.
Sam has a fair amount in common with him, despite their age difference. I can see a casual friendship that was maybe struck over books in the coffee shop?