The process of critical thinking or teaching of these skills are possible in schools, but I think what is attempted should be called clearer thinking. I would leave critical thinking in the realms that call for challenging accepted knowledge. I don't think this occurs often in schools.
An excellent article in California Educator, June 2009, describes how some teachers are teaching clearer thinking by ways of organizing thinking. I will mention a few of these and whenever you are teaching or discussing any reading you can add these to your repertoire.
Dr.Christianna Alger states that asking the right questions may build a critical thinking classroom. (Many of the times you see baffled looks from students is due to the question not being clearly stated or it is not the correct question for the answer that you believe is right.)
CLARITY. Can you state that in a different way? Can you elaborate on what you said? Can you give an example? Is there another word or phrase that communicates the problem?
ACCURACY. How do we check to see if that statement is valid? How do we know it is correct? Where did you get the information? How can we verify or test it? (This is less of a problem when the sources are known and controlled by the teacher or district, but does it allow for challenges?)
DEPTH. What factors make this a difficult problem? What are some of the complexities inherent in this problem? (We tend to go towards simple answers.)
RELEVANCE. How does that relate to the problem? How does that help us with the issue?
FAIRNESS. Do you have a vested interest in this issue? Are you sympathetically representing the relevant viewpoint of others? (This gets to the heart of my objection in calling it critical thinking. Is the student able to present a radically different viewpoint without it conflicting with what the teacher wants, believes is correct, or will accept?)
Jeffrey Lantos, LA District, uses plays and songs to reenact what they read and research. (Plays and songs stimulate more of the brain than quiet reading does.)
Betty Lightfoot, Lake Elsinore district, uses, "Thinking maps." These were developed Dr.David Hyerle. A circle map shows context. A flow map demonstrates sequencing and a tree map classifying, grouping. (This is very helpful when you want an outline or a summary. I see these and many others in use at every level of education and they do make it easier for students to organize their thinking.)
Mira Blazy, Palm Springs District, uses manipulatives and experiments in her 8th grade science classes. Jack Stafford, same district, uses students to correct papers. They have a rubric to follow and usually they evaluate the papers from a different class. (I struggled for years experimenting with ways to make my rubrics easy to use and still get students to grasp the most important elements in thinking through and communicating their message.)
The above are all useful ways to get more skill practice and more content from any reading by offering them different approaches that keep them motivated. They work well. (My teachers are using these with the novel, Rick and Bobo.)
In my recent book, Abuses of Power in Education: Challenging Practically Everything, I explain how power differences (inequalities) make education more difficult than it needs to be. Mr. Stafford's excellent use of students correcting papers won't work with some teachers. I used that technique throughout my career and I was told I was lazy (true), the kids couldn't do it (untrue), and it would create discipline problems in the class (true unless the teacher creates a safe classroom and teaches the students how to do the corrections.)
The main reason it doesn't work is when there is no trust between the teacher and students. There has to be a sense that if a student is angry about the correction that it can be handled civilly and fairly. This doesn't happen unless the students are part of the planning before any correcting occurs.
When teachers are reluctant to share their power the students doing the correcting feel (and are) used. When students use and apply the rubrics in correcting others' papers it becomes a valid teaching technique! Negotiating and sharing power builds mutual trust and respect. When teachers try this method the students don't believe them. They abuse their new powers and the teacher gets defensive and angry and returns to his power position. I tell students that I know some of them don't trust me and it'll take some time for me to prove I am willing to take the time to show them how this will improve their lives.
I took this technique as an example, but it is true of any of the complex relationships in school between any individuals or groups. Each needs the power to do the job with minimal interference from those with more power. However, when power is shared, then accountability for behavior goes with it.
When I say I'm sharing power, I emphasize that they are sharing responsibility for outcomes. Once they discover I mean it (I follow through with the consequences they believe fit the offense) and they have more real freedom most accept their part of accountability.
This brings me to the meat of my concern and doubt that schools do teach critical thinking. They can teach the process as I have shown some are doing, but without sharing of power they cannot teach students to think critically. If the teacher has to constantly worry that anything he says may offend someone and it could mean his job or minimally harassment, why should he deal with controversial thoughts? It's easier to teach the process and use known and agreed upon, safe answers and topics.
The areas most upper grade and secondary students are concerned about are social relations, sexuality, religion, and to a lesser degree politics. All these things are taboo!
In Los Angeles in 1961 teachers were not allowed to discuss communism. I taught all the various forms of government knowing I was courting trouble. The PTA President had her sixth grader in my class. She told me the PTA had discussed what I was doing and stated they'd back me if anything happened. Nothing did because I gave my honest appraisal of each type's strengths and weaknesses. Our discussions in class were wild and exciting and continued into their homes (mostly lower middle class). My students understood why some people so strongly believed in their political system without them trashing their own.
From 1986 -1995 I ran an at-risk program for the most dysfunctional fifth to eighth graders in our district (many had failed one to three times). I had hour-long intake interviews and told the parents that I would answer ANY questions the students asked. If they came home and the parents were upset by what I had said they (or anyone that represented their viewpoint) could come in and discuss it with me in front of the class. They understood that the class could challenge them like they did me. Some of their questions and discussions would have made Jerry Springer blush (another reason teachers shy away from this).
In both (and all) settings I created a classroom environment that didn't merely tolerate differences of opinion I encouraged it! We had discussions every day and they dealt with the curriculum too, but they knew they could bring up the topics that were most important to them.
This does not and cannot happen in the way our schools are structured with their hierarchical power base that punishes thinking that differs from the status quo. For that reason I repeat we can teach the process and skills of clearer thinking, but we can't teach them to think critically and apply those skills to the real worlds they live in. It goes against too many vested interests that fear their power will be diluted
Until teachers have the freedom to teach using the best of their abilities without fear of job loss or constant harassment and students have the freedom to honestly, civilly disagree there cannot be critical thinking.