Can you recommend math and study help video publishers for reviewing difficult concepts for school?

Absolutely — here are some strong math and study-help video publishers/channels that are great for reviewing difficult school concepts.

Math-focused video publishers

• Khan Academy — Clear, step-by-step explanations for algebra, geometry, calculus, statistics, and more.
• PatrickJMT — Very concise math problem walkthroughs, especially useful for practice problems and exam review.
• Professor Leonard — Excellent for deeper understanding, especially pre-calc, calculus, and college math.
• The Organic Chemistry Tutor — Despite the name, he covers a huge range of math topics, plus physics and chemistry; very helpful for homework help.
• Math Antics — Great for middle school and early high school math with simple explanations.
• Eddie Woo — Strong explanatory style for secondary-school math concepts.
• 3Blue1Brown — Best if you want intuitive visual understanding of concepts like calculus, linear algebra, and neural nets.
• Numberphile — More conceptual and curiosity-driven; great for building interest in math.

General study-help / learning skills channels

• Ali Abdaal — Study strategies, productivity, note-taking, and exam prep.
• Thomas Frank — Study systems, focus, memory, and student productivity.
• How to Study for Exams / exam-prep style channels — Many schools/educators post specific revision strategies and problem-solving tips.
• CrashCourse — Good for broad subject review in a fast, engaging format.

Best picks by need

• Need quick homework help: Khan Academy, PatrickJMT, The Organic Chemistry Tutor
• Need deeper understanding: Professor Leonard, 3Blue1Brown
• Need easier beginner explanations: Math Antics, Eddie Woo
• Need study habits and exam prep: Ali Abdaal, Thomas Frank

If you want, I can also make you a short list by school level:

• middle school
• high school
• college
  or by topic like algebra, calculus, statistics, geometry, and SAT/ACT prep.