I always struggle with this b/c I feel like perhaps mine aren’t spending enough time on school but then when i look back at all they’ve done … I don’t really worry about the times as much. Totally get the need though to take stock of it.
My 7th grader spends from 3-4 hours most days, closer to 4 most days. He does Group learning every day. Ours is usually 30-45 minutes, mainly b/c I have 3 little ones and that is all we can reasonably do with them (and I do require them to all sit in even with an activity or crayons and paper or a map to color, etc.).
Often though, before group time, if he wakes early enough, he will have already done his morning chores and begun indepdendent work:
Bible study (we attend Community Bible Study so he is working on the Book of Acts through that this year)
Math (combination of Saxon, IXL problems, Khan Academy, Games, etc.)
Independnet Reading for 45 minutes (this is NOT to include reading for science but does include assigned history readings)
Science (on Tuesdays and Thursdays only; right now he is using the Geology Book we found on the book list here; he likes it and so do i b/c he likes it; science is just not going to be a subject of interest for him once he doesn’t have to do it)
History Reading (see above; this is the book he has currently assigned that compliments our Group History lessons)
Language (on any given day, he is using Grammarlogue lessons, working on a historical fiction novel he is writing, doing a lesson in Rod&Staff Book 7; a lesson in The Write Stuff Adventure or The Fallacy Detective; he does different assignments on different days and for the most part is student-led on this).
In addition to all of this, he works independently on his Scout Merit Badges and most often these are learning experiences, so we count it. He has learned a lot actually and is motivated so that is the key on it. He also loves LEGO building and is always working on another design (he designs from scratch). He will often take a photo of an airplane or something else he builds and include that in his current novel by scanning it in as an image.
He recently built us a compost bin totally on his own. He cross-stitches, though like his Momma he prefers to do this when the weather turns cold outside so not as much lately. He has recently developed more of an interest in photography.
He READS a lot about WWI history. He is not crazy about the history time period we are in (and neither am I), but he goes along with it and looks forward to when we move into more modern history. I am determined to go through it all though b/c I got to World History in HS and college and really struggled. I had no exposure prior to high school. Even my two 6YOs can tell people a lot about ancient history!
I guess that is about it. Oh and our 4th grader spends probably 2-3 hours on book work, much like above except he has shorter reading time requirements and shorter math lessons. I don’t really worry about reading with our children b/c they all love to read and often stay up too late reading! 
Hope this helps!