My son is almost 4. We have a starfall subscription which he enjoys at times (it's got good variety and allows learning across various areas within a topic (such as math - add/subtract, weight, length etc).

We also have a www.mathseeds.com subscription which is meant for 3-6yr olds (my son started this before 3 easily). While it's a good program (I was looking for something to teach numbers above 10 and the basics of add/subtract) it's ordering of things (at least for my son) is a bit weird imo. They introduce addition very early on (even up to 20) before concepts like near/far, long/short. This particular website is based on a progression so you must pass each level before moving onto the next. They have tests at the end of each map (5-10 levels each) They offer a 2-4 week trial (depending on where you are and where you sign up from) and you can do a placement test.

The creators of mathseeds also do www.readingeggs.com which is also subscription based (if you sign up for a free trial you have access to both). This program is by far the best learn to read program ive come across. It's very comprehensive. It works on phonetics AND sigh words together as well as spelling pretty early on. Once you're further into the program (map 5 I think) they add even more content and a heap of early readers your child can read then gets tested on the comprehension.