I was recently listening to an interview with the Skeptic Rhys Morgan, on the Young Australian Skeptics podcast. They discussed science teaching in school, and how critical thinking doesn't get much attention; and he mentioned an experiment involving the rather un-rigorous practice of continuting to gather results until you get the answer you want.
My own experience of being taught science at school was, on the whole, quite good I think. I'd always enjoyed science, so was pretty receptive to the topics we covered. However, like Rhys I also noticed a lack of proper experimental rigour, with the main objective being learning a collection of facts. Not that learning lists of facts, to regurgitate under exam conditions, was all we did - generally the reasons behind things were explained, and we got a reasonable understanding of the topics, and I think we got what could be considered a reasonable science education. What was missing though was an understanding of why we know these things, and the process of rigorous experimentation by which science is done: in short, there was a conspicuous absence of the actual scientific method.
There were even, occasionally, situations like the above, in which experiments are carried out seemingly in order to show that we've done it and got the result we expected, rather than to find something out. I remember one chemistry practical in particular, where after gathering one set of results, we were told about how it's important to repeat results to confirm them and combine the results (great so far); but then since we didn't actually have time for that, to just make up some data points for more runs, such that the average was pretty much in agreement with the original data. I can't even remember if it was stated that this is or isn't what you're meant to do, and it gives a terrible impression of how science works. Basically: we can make up results to confirm what we think is true. Shudder.
This might have been an isolated incident; but then so were practicals generally. I can only speak for Physics, since I didn't do the others beyond GCSE, but A-Level experiments also mostly consisted of measuring results, plotting graphs, and noting how it obeyed Hooke's spring law or whatever. I don't remember much at all about hypothesis testing, accumulation of evidence, how a theory is confirmed or discarded, and so on (though to be fair, the insistence that we only change one variable at a time to isolate its effect made a lasting impression).
For people who are already intending to pursue science as a career this will be rather annoying, even misleading; but something that will surely be learned or picked up with further study. The greater shame is for those who are only tangentially interested, and go on to pursue other things. If this is how science is taught, without really getting to the bottom of what makes the scientific method so powerful, it is no surprise that people often don't appreciate scientific inquiry for what it is, or downplay its relevance to life in general. Without this introduction to critical thinking and skepticism, people aren't going to hold ideas to the scrutiny they require - which leads to a lot of the problems that exist today. The efforts of the skpetical community to counter such nonsense as homeopathy, religion, and magic jewellery just go to show how little rationality is embedded in our culture and education. In fact I'd say I've learned a lot more about the scientific method from the skeptical blogs and podcasts than from being taught actual science.
Interestingly, there was one subject at school which did put a strong emphasis on being critical of the source of information and its veracity: history. It's strange, now, to consider the contrast, especially in a field not usually noted for its experimental rigour. But for what seemed like forever we were evaluating the reliability of sources, discussing the merits of first hand versus second hand information, examining the biases in what certain records might have shown. Proper scientific thinking, from an entirely unexpected direction. Unfortunately I found this incredibly dull, and couldn't wait to get to the actual interesting bit of stuff that actually happened - I had no patience for all this questioning and weighing up of sources... oh well.
One could argue (in spite of the history thing) that the details of the scientific method aren't going to hold the attention of children, and its important to focus on getting some basic facts into them. But I disagree with this: yes, the fact that stuff accelerates in a gravitational field, that cats can evolve into dogs (note: satire), and that magnesium is really sparkly are all important lessons to be learned. However, children's ability to forget things when they are no longer examined is most impressive, while being taught how to think critically and to carefully examine the world to determine what is real should be essential life lessons. Perhaps the most important skill for children, or indeed anyone, to learn, is how to ask proper questions, and how to understand if they are getting a proper answer.