I am at that level and the two books so far that have been the most help are:
Logical chess
https://www.amazon.com/Logical-Chess-Every-Explained-Algebraic/dp/0713484640/ref=asc_df_0713484640_nodl/?tag=hyprod-20&linkCode=df0&hvadid=266117255231&hvpos=1o1&hvnetw=g&hvrand=1998381252751757257&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9019795&hvtargid=pla-457758300691&psc=1
And
Best lessons of a chess coach
https://www.amazon.com/Lessons-Chess-Coach-Sunil-Weeramantry/dp/0812922654
This is the one I used to get my end game to acceptable level
https://www.amazon.com/Silmans-Complete-Endgame-Course-Beginner/dp/1890085103
It did the job, and the chapters are sorted by player level. Meaning you can just do the first few chapters and then go back to focusing on your tactics and middle game. Which is what I did.
Browse here....lots of good book suggestions for players at those levels....
Beginners Chess Courses, Lessons, Instructional Resources...
https://www.chess.com/blog/RussBell/beginners-chess-course-instructional-resources
and more...
https://www.chess.com/blog/RussBell
Chess Steps Method (Stappenmethode) and Chess Tutor discs (same folks) ...
Level 1 workbooks and Chess Tutor level 1 CD is through rating 800 (USCF)
Level 2 workbooks (Step 2, Step 2 Plus, Step 2 Extra, Step 2 Thinking Ahead, and Step 2 Mix) and Chess Tutor level 2 CD is through rating 1400 (over 4000 problems to solve, combining workbooks and CD)
Level 3 workbooks and Chess Tutor level 3 CD is through rating 1600 (over 4500 problems to solve combining workbooks with CD)
Level 4 is workbooks (no CD) through rating 1750
Level 5 is workbooks through rating 1900
Level 6 is workbooks through rating 2100
https://web.archive.org/web/20140708104437/http://www.chesscafe.com/text/logichess.pdf
https://www.reddit.com/r/chess/comments/73r6j4/review_best_lessons_of_a_chess_coach_by_sunil/
https://web.archive.org/web/20140708103149/http://www.chesscafe.com/text/review594.pdf
https://www.silmanjamespress.com/shop/chess/silmans-complete-endgame-course/
http://theweekinchess.com/john-watson-reviews/theres-an-end-to-it-all
https://chessbookreviews.wordpress.com/2014/11/16/the-chess-steps/
Here are some reading possibilities that I often mention:
Simple Attacking Plans by Fred Wilson (2012)
https://web.archive.org/web/20140708090402/http://www.chesscafe.com/text/review874.pdf
http://dev.jeremysilman.com/shop/pc/Simple-Attacking-Plans-77p3731.htm
Logical Chess: Move by Move by Irving Chernev (1957)
https://web.archive.org/web/20140708104437/http://www.chesscafe.com/text/logichess.pdf
The Most Instructive Games of Chess Ever Played by Irving Chernev (1965)
https://chessbookreviews.wordpress.com/tag/most-instructive-games-of-chess-ever-played/
Winning Chess by Irving Chernev and Fred Reinfeld (1948)
https://web.archive.org/web/20140708093415/http://www.chesscafe.com/text/review919.pdf
Back to Basics: Tactics by Dan Heisman (2007)
https://web.archive.org/web/20140708233537/http://www.chesscafe.com/text/review585.pdf
https://www.chess.com/article/view/book-review-back-to-basics-tactics
https://static1.squarespace.com/static/5856bd64ff7c50433c3803db/t/5895fc0ca5790af7895297e4/1486224396755/btbtactics2excerpt.pdf
Discovering Chess Openings by GM John Emms (2006)
https://web.archive.org/web/20140627114655/http://www.chesscafe.com/text/hansen91.pdf
Openings for Amateurs by Pete Tamburro (2014)
http://kenilworthian.blogspot.com/2014/05/review-of-pete-tamburros-openings-for.html
https://chessbookreviews.wordpress.com/tag/openings-for-amateurs/
https://www.mongoosepress.com/catalog/excerpts/openings_amateurs.pdf
Chess Endgames for Kids by Karsten Müller (2015)
https://chessbookreviews.wordpress.com/tag/chess-endgames-for-kids/
http://www.gambitbooks.com/pdfs/Chess_Endgames_for_Kids.pdf
A Guide to Chess Improvement by Dan Heisman (2010)
https://web.archive.org/web/20140708105628/http://www.chesscafe.com/text/review781.pdf
Studying Chess Made Easy by Andrew Soltis (2009)
https://web.archive.org/web/20140708090448/http://www.chesscafe.com/text/review750.pdf
Seirawan stuff:
http://seagaard.dk/review/eng/bo_beginner/ev_winning_chess.asp?KATID=BO&ID=BO-Beginner
http://www.nystar.com/tamarkin/review1.htm
https://web.archive.org/web/20140627132508/http://www.chesscafe.com/text/hansen173.pdf
https://www.chess.com/article/view/book-review-winning-chess-endings
https://web.archive.org/web/20140708092617/http://www.chesscafe.com/text/review560.pdf
I am looking for books recommendation to teach specifically between this level.
I have books of all this topics for higher levels , but i need some easy ones for kids to help teach them in a school.
Endgames is not necessary but i also appreciatte any advices.
Thank you in advanced.