Science is messy. It is an excellent, fun, complex subject. However, unless you read a textbook and fill out worksheets (in which case it will not be excellent, fun, or complex), then it is messy.
Experiments are messy. Expect to have to clean up goo.
Even if you don’t have to clean up goo, expect to have to take the time to compile an odd assortment of things. It will be weird, random stuff and it will often be stuff that, if only you had realized you were going to need this random stuff, you could have saved it months ago, except you couldn’t imagine you would ever need it, so you recycled it.
Even if you get a kit, expect that it will have bits and pieces and that when it’s time to experiment you’ll have to cook up and cool the agar or paint the volcano shell and soon there will be goo to clean up anyway.
Going outside is messy too. Expect to have to scrape off mud after bird watching, tadpole collecting, water testing, and bug observing. Expect to not find what your lesson suggested you find out in nature and instead find something completely different.
Even if you don’t want to do experiments or go outside, textbooks are boring while science books and videos for kids are anything but boring. So if you want to read interesting science, you have to have a messy pile of books and DVD’s in different formats without pre-prepared review questions and color in worksheets.
So stop asking for a science curricula that fits into a neat little box the way your grammar program does or the way your math program does. Those things can fit into boxes and science simply does not. Math can be “open and go” or “do the next thing.” Science doesn’t play that game. It will always require you to do prep work or roll with the unexpected. The more you try to force it to be neat and tidy and simple, the more boring you’re forcing this interesting subject to become.
PS – Take chances, make mistakes, get messy!
PPS – It’s just me, but I felt like it’s what Ms. Frizzle would tell you if she posted on homeschool forums.