Students at Whitin Intermediate have access to ST Math through Clever.com. I have also added Code.org, Whoo's Reading, and typing in the CLever homepage.
The list below are free websites that support math learning and practice. I will add descriptions of the sites and grade levels, but please look at sites other than your child's grade level. There are some great sites that will challenge your children. Productive struggle is important.
Some sites below come from the National Council of Teachers of Mathematics and are interactive for your children. Other sites are interactive.
Khan Academy for tutorials https://www.khanacademy.org/
Subitizing, or the ability to quickly recognize numbers, is an important skill. The 3 links below, using 5 and 10 frames, help children recognize numbers quickly, and see what numbers compose either 5 or 10.
5 frame practice: http://illuminations.nctm.org/Activity.aspx?id=3564
10 frame practice: http://illuminations.nctm.org/Activity.aspx?id=3565
10 frame practice http://gregtangmath.com/tenframemania
Fraction games: https://www.nctm.org/Classroom-Resources/Illuminations/Interactives/Fraction-Game/
https://www.nctm.org/Classroom-Resources/Illuminations/Interactives/Playing-Fraction-Track/
https://www.nctm.org/Classroom-Resources/Illuminations/Interactives/Fraction-Models/
https://www.nctm.org/Classroom-Resources/Illuminations/Interactives/Equivalent-Fractions/
https://www.mathplayground.com/index_fractions.html
Coin counting grades k-2, 3-5 http://illuminations.nctm.org/coinbox/
multiple addends to find a sum grades 3-5, 6-8 http://illuminations.nctm.org/DeepSeaDuel/
Balancing equations using numbers grades 3-5 https://illuminations.nctm.org/Activity.aspx?id=3530
Balancing numbers using shapes grades 3-5, 6-8 https://illuminations.nctm.org/Activity.aspx?id=3531
Bar Modeling grades 2+ http://www.mathplayground.com/thinkingblocks.html
Greg Tang Numtanga matching pictues/words/numbers starting at 0-20 and moving to fractions and measurement http://gregtangmath.com/numtanga
Algebra for all, starting in grade 1! https://graspablemath.com
Math problems with support grade 4+ http://tutor.mathspring.org/ms/welcome.html
Website with different levels of problems from the University of Cambridge http://nrich.maths.org
Greg Tang http://www.gregtangmath.com/games
https://www.mathplayground.com/
http://www.sheppardsoftware.com/math.htm