Congratulations on completing the 250 box challenge!

I've noticed your boxes have definitely improved from the 103rd box onwards, as there are less parallel lines and you cleared the line extension mistake from box 12. You still have the occasional diverging line, but you are largely much more consistent by the end. You did a good job practicing foreshortening through a variety of orientations and proportions. Doing this helps you have a well rounded understanding of how boxes will behave in different situations. Your line work is looking clean and confident as well, you plan out your lines and show that you're using the ghosting technique. Did you apply line weight? because I didn't notice it, you want to apply it subtly and to maintain your confidence while drawing the additional line, accuracy will come with mileage. I can't really tell how large your sketch book is but, drawabox recommends using A4 sized paper (21.5 x 28 cm) or (8.5"x11"). This allows you to draw your boxes as large as possible, this helps us get used to using your shoulder and helps you see your mistakes more clearly. However, if you are limited to the sketch book don't worry about it.

Your boxes may not be perfect, don't expect them to be. The important thing is they're more consistent. I'll be marking your submission as complete so you can move on to lesson 2.