Hi!
You have a good hang of the gestures, they capture the movement well and it makes them look realistic, even when time is short. This is why it's good that you complete the gestures for 30 and 60 seconds, where the action or inaction matters more while perspective and proportions should be instinctive only. I see you mark the direction of the chest, which is good, although there's no gesture line that marks the general direction of the body, the direction in which the force is applied. You line the body up in believable poses anyway, but try capturing the flow of force in a line and I think you'll see a difference. This is the line you're fitting the rest of the body along later.
In your longer poses you focus on the outline. I'll recommend you watch Proko's video series on gesture drawing. The concept he teaches is called constructional drawing, it means you draw as if you were constructing a building. Effectively building from the gesture up, the gesture becomes forms, the forms are assigned weight and become volumes. Looking at your longer studies I think you're going on to rendering the skin rather quickly, hurriedly placing the forms and misjudging proportions. You might want to think about deciding before going into the class if you want to work on rendering what we see the body as - so you can do shading and lighting practice - or if construction of the body, which Proko's videos are good for, is the focus of the day. Generally when you work with forms, you don't shade them but let them connect and intersect in ways that can tell how they are placed. I wouldn't tackle lighting in a constructional drawing though.
Good luck!
