Lonni

https://www.mangago.me/read-manga/story_telling_business/

https://www.mangago.me/read-manga/so_who_got_screwed/

https://www.mangago.me/read-manga/glasses_cloth_and_playlist/

https://www.mangago.me/read-manga/hang_out_crisis/

have you read cherry blossoms after winter

Yes

Okay so here's peak for ya
https://www.mangago.me/read-manga/nagahama_to_be_or_not_to_be/

do you need childhood friends? i will give you childhood friends!
https://www.mangago.me/read-manga/the_drastic_love_in_midnight/ (it has a prequel one shot as well that shows their high school dynamic)
https://www.mangago.me/read-manga/i_declare_vengeance/ (they're childhood friends but MC doesn't remember ML now)
https://www.mangago.me/read-manga/the_nameless_flower/ (angst and yearning final boss, you need to read this if you want to cry, completed but not exactly. probably will get more side stories i am hoping)
https://www.mangago.me/read-manga/home_ep/ (a country side/city life BL where two childhood friends who lived in countryside. now one of them is an actor so lives in seoul but visits from time to time)
https://www.mangago.me/read-manga/dogusare_dandies/
https://www.mangago.me/read-manga/omae_no_koi_wa_ore_no_mono/
https://www.mangago.me/read-manga/so_who_got_screwed/
https://www.mangago.me/read-manga/the_omega_takes_a_husband/
https://www.mangago.me/read-manga/cottage_garden/ (that one yaoi with british dialogue lmao. i love it personally, have reread it like 3-4 times for feel good purposes)
https://www.mangago.me/read-manga/naked_sword_and_tree_peony_of_black/ (yes i glaze this manga all the time, no i don't take criticisms about this. yes I have reread this quite a few times and i savour it every single time, i am the perpetuator of the cult which preaches this manga. hyperbole haha, but you get how much i love this)
https://www.mangago.me/read-manga/mousetrap/
https://www.mangago.me/read-manga/unchanged_man/ (creepy so creepy but it's really good psychological manhwa. you need to get on this one)
https://www.mangago.me/read-manga/introducing_my_manager/
https://www.mangago.me/read-manga/gunjou_no_subete/

OOO THANKS

oh sorry i did not read the title of your question. i js read "childhood friends" and ran with it.
some of them are not highschool BLs, and the protagonists are well into their adulthood, while some are still in highschool. they all have common childhood friends to lovers trope though. i'm sorry. just check which ones you like. personally, all of them are great. (lmao I'm rooting my own horn, i got peak taste what can I say lmao)