TI Smart Space: A video series designed to set students up for success in core math and science courses. These lessons are great for both in-person and virtual learning.
A few math-related Youtube channels:
Mind Your Decisions: "brain teasers, riddles, logic puzzles, viral math problems, and math topics from viewers around the world." Includes solution approaches for various test and contest mathematical puzzles and problems. Generally at pre-calculus le
3 Blue 1 Brown: "by Grant Sanderson, is some combination of math and entertainment, depending on your disposition. The goal is for explanations to be driven by animations and for difficult problems to be made simple with changes in perspective."
Mathologer: "Enter the world of the Mathologer for really accessible explanations of hard and beautiful math(s)."
Numberphile: Videos by various presenters on interesting mathematics problems, some including current research and unsolved problems.
The Organic Chemistry Tutor: This channel focuses on providing tutorial videos on organic chemistry, general chemistry, physics, algebra, trigonometry, precalculus, and calculus."
Khan Academy offers a variety of math and science courses. You can register as a student, teacher, or coach. These have been offered as an alternative to in person or locally created remote courses in some Vermont schools.
Brilliant.org offers self-paced courses in various math and science topics. Some courses required a paid subscription.