Free interactive STEM activities that you can filter by science, mathematics, or grade level. (OER)
Crash Course has a series of videos to teach a variety fo statistics concepts.
GeoGebra is mathematics software for algebra, geometry, statistics, and calculus. There is a calculator suite for graphing, 3D, geometry, and probability. There are tutorials that explain how to use all the calculator features.
Khan Academy has free online courses, lessons, and practice. They have resources for statistics, calculus, algebra, trigonometry, and geometry!
PhET Interactive Simulations provides access to a library of simulations to teach math concepts and applications. Results can be filtered by grade level, subject, language, and accessibility features. (OER)
You do have to make an account to access flexbooks, but it is free and considered an OER. Once you have selected a text book you can distribute it as is to students, or customize the content to suit your needs. 2.0 textbooks are interactive and allow students to take notes. There are textbooks for a variety of grade levels, and some are even available in Spanish! They have courses on life science, earth science and physical science. (OER)