I don't have actual experience with it directly yet, but I have been looking over the material for a few months trying to decide if it is a good fit. From what I've gathered, the material available on the site can be divided into either units (http://www.sciencelearningspace.com/study-units/) or grade level (http://www.sciencelearningspace.com/grade-levels/). If you choose the unit option (best in middle school), your student will progress through the 20 units at their own pace. I assuming all the units will take maybe 2-3 years....but I'm really not sure. If you choose the grade level option, your student will go through a few topics (2-4) selected specifically for that grade. I am not sure if these topics would span 150-180 hours required by my state for one year of science, so if using the grade level approach, id imagine there would be a lot of extra reading and activities. I don't mind this though. I think adding in living books and nature exercises would work for us.
The curriculum itself covers all the topics your students need to learn in science including Physics, Chemistry, Earth Science and Life Science. The structure of the material is laid out pretty well. Each broad topic is dividing into smaller topics. Each smaller topic has and intro video and text reading to explain the concept, then several different videos with hands-on experiments to test and learn the topics more thoroughly. After that there are usually some pdfs to print and record findings or to further cement the info.
i.e. The first unit is called Mechanics. It's divided into three smaller topics: Force, Gravity and Friction. The second unit is called Motion and it's divided in velocity and acceleration, etc.
The Pros: (1) Covers all middle/elementary science topics, (2) has a lot of printables, (3) has video instruction we can watch together, (4) has many hands-on experiments.
The Cons: (1) The topics in the grade level option don't cover the required learning time. While the topics do cover everything you need to learn, in theory, you could do all the videos pretty fast. The parent will probably need to incorporate some extra material or ideas to make it last all year. If using the grade structure, i'd suggest organizing the each topic into 9-12 week unit studies or something similar.
Overall, I think this is an awesome curriculum and I think I will def be using it. The hands-on nature of the lessons and the videos really sell me.
I'm not an expert on the program though, so check out the link and watch some of the videos. You'll also be able to see the lesson structure on the site.