Sorry for the huge list and hopefully one peaks your interest ;w;
@KatoShuu Were you thinking of this one? https://mangadex.org/title/23523/hosaka-sensei-no-ai-no-muchi
https://mangadex.org/title/868/minami-ke Each sister is in a different grade so it covers elementary, middle, and high school. Slice of life, comedy
Elementary School:
https://mangadex.org/title/34802/kitsune-to-pancake Slice of life, comedy, fantasy. This one is more fluff and about half animal girls and how their single fathers raise them. It does take place in school sometimes
https://mangadex.org/title/24212/my-home Slice of life, comedy. Mai, an elementary school girl, takes care of her childish father and it focuses on their everyday life and the antics that occur. Some characters from Munko's other works appear in the manga and I recommend reading their other works!
https://mangadex.org/title/12093/amaama-to-inazuma Slice of life, drama, cooking. It covers from preschool/kindergarten to elementary school. There are also high school students, but it mainly focuses on the child.
https://mangadex.org/title/14615/nekota-no-koto-ga-ki-ni-natte-shikatanai Comedy, drama, romance, mystery. Mikki starts as an elementary school transfer student and it follows to her middle school years. The interesting twist is that she sees her classmate, Nekota, as a cat! It focuses on the relationships in the classroom and how she starts to unravel why she sees only him as a cat.
Middle School:
https://mangadex.org/title/14508/hitoribocchi-no-seikatsu. Slice of life, comedy. It focuses on friendship and hilarious shenanigans that occur
https://mangadex.org/title/22281/misoshiru-de-kanpai. Slice of life, romance, comedy. Really nice feels good food manga that will give you a lot of information on miso! Doesn't really focus on the school aspect.
https://mangadex.org/title/28834/saeki-san-wa-nemutteru. Slice of life, romance, comedy. Cute, comedic, and feels good shenanigans that involve various ways to fall asleep in class.
https://mangadex.org/title/9842/love-lab. Slice of life, romance, comedy. Hilarious shenanigans of girls from an all girls school trying to figure out how to prepare for future romance, but have zero experience. The scanlators have chosen to start uploading from after where the anime ends so you will need to find the raws or watch the anime first (12 eps?) and continue from there. But I highly recommend it anyways because it's worth watching the stupid things they go through XD
https://mangadex.org/title/19736/nanairo-kakumei Drama, school life, psychological. It does a really good job of depicting middle school bullying, but it will test your patience at times...it's pretty infuriating. But you will see Nana's character development as she figures out who she is, where she belongs, and stands up for herself.
Veterinary College:
https://mangadex.org/title/3131/doubutsu-no-oishasan. Slice of life, comedy. Focuses on the character's struggles of becoming a vet and his husky. The art style is a bit old, but it's pretty informative with...dynamic characters.
Patissiere School:
https://mangadex.org/title/8927/yumeiro-patissiere Comedy, romance, fantasy. Takes place in middle school for those training to become patissieres. It focuses on Ichigo's struggle to catch up to the rest of the group who have been going to the school/practicing from a young age.