US: Is there any subject that it is unlawful to teach in schools?

Question

In the US, are there any laws that restrict certain subjects or topics, or parts thereof, from being taught in schools?

Answer 1

A teacher could not instruct students in how to build explosives for use in Federal crimes:

It shall be unlawful for any person to teach or demonstrate the making or use of an explosive, a destructive device, or a weapon of mass destruction [...] with the intent that the teaching, demonstration, or information be used for, or in furtherance of, an activity that constitutes a Federal crime of violence (source)

This Federal statute creates a law preventing the teaching (in any context, including schools) of bombmaking for the purpose of committing a federal crime.

So "bombmaking" is one subject that cannot be taught, although I don't think that there have been any prosecutions of regular K12 teachers under this law.

Answer 2

In 1925 Tennessee passed the Butler Act, which prohibited the teaching of evolution in public schools, more specifically the teaching that "mankind was descended from a lower type". This law was challenged in the famous Scopes Trial, more formally The State of Tennessee v. John Thomas Scopes, often known as the 'Monkey Trial".

Scopes was convicted and fined, but the conviction was overturned on a technicality: the $100 fine was set by the judge, not the jury, but under Tennessee law at that time, a judge had no power to impose a fine over $50 without it being set by the jury. However, the Tennessee Supreme Court found that the Butler Act was Constitutional.

The law remained on the books, and similar laws in some other US states, until the 1960s. In * Epperson v. Arkansas* 393 U.S. 97 (1968) The US supreme court held that such laws violated the Establishment Clause of the US Constitution, because their purpose was religious. The court wrote:

The overriding fact is that Arkansas’ law selects from the body of knowledge a particular segment which it proscribes for the sole reason that it is deemed to conflict with a particular religious doctrine; that is, with a particular interpretation of the Book of Genesis by a particular religious group.

...

[T]he state has no legitimate interest in protecting any or all religions from views distasteful to them.

Such laws were only rarely enforced while they were in place, but some scholars argue that they significantly influenced textbook contents and the way in which high-school biology was taught.

Also, according to this news story from the Texas Tribune Texas has recently passed a law on the teaching of history, said to be designed to prevent the teaching of "Critical Race Theory" among other things, although the law does not explicitly mention that theory. The law, known as HB 3979, amends Section 28.002 of the Texas Education Code. It requires teaching various topics including "an understanding of ... the founding documents of the United States" which it lists as including the Declaration of Independence, the US Constitution, the Federalist papers, and the Lincoln-Douglas debates, among others.

The law provides in section (h-3)(1) that:

a teacher may not be compelled to discuss a particular current event or widely debated and currently controversial issue of public policy or social affairs

It also says in (h-3) (4) (B) that a school or teacher may not:

require or make part of a course the concept that:
(i) one race or sex is inherently superior to another race or sex;
(ii) an individual, by virtue of the individual ’s race or sex, is inherently racist, sexist, or
oppressive, whether consciously or unconsciously;
(iii) An individual should be discriminated against or receive adverse treatment solely or partly because of the individual’s race;
(iv) members of one race or sex cannot and should not attempt to treat others without respect to race or sex;
(v) an individual ’s moral character, standing, or worth is necessarily determined by the individual ’s race or sex;
(vi) an individual, by virtue of the individual’s race or sex, bears responsibility for actions committed in the past by other members of the same race or sex;
(vii) an individual should feel discomfort, guilt, anguish, or any other form of psychological distress on account of the individual’s race or sex
...
(x) with respect to their relationship to American values, slavery and racism are anything other than deviations from, betrayals of, or failures to live up to, the authentic founding principles of the United States, which include liberty and equality;

So those teachings are currently prohibited by law. The law has not yet been implemented nor tested in court.

Answer 3

Just from recent news I know that Critical Race Theory

Critical race theory (CRT) is a body of legal scholarship and an academic movement of US civil-rights scholars and activists who seek to critically examine the intersection of race and U.S. law and to challenge mainstream American liberal approaches to racial justice.1​2[4] CRT examines social, cultural, and legal issues primarily as they relate to race and racism in the US.[5][6]

is legislated against in certain states in the US, and banned by the school boards in more.

• Eight states (Idaho, Oklahoma, Tennessee, Texas, Iowa, New Hampshire, Arizona, and South Carolina) have passed legislation.
• None of the state bills that have passed even actually mention the words “critical race theory” explicitly, with the exception of Idaho.
• The legislations mostly ban the discussion, training, and/or orientation that the U.S. is inherently racist as well as any discussions about conscious and unconscious bias, privilege, discrimination, and oppression. These parameters also extend beyond race to include gender lectures and discussions.

All the relevant legislation is linked from the article. The Idaho legislation explicitly mentions Critical Race Theory.

(2) The Idaho legislature finds that tenets outlined in subsection (3)(a) of this section, often found in "critical race theory," undermine the objectives outlined in subsection (1) of this section and exacerbate and inflame divisions on the basis of sex, race, ethnicity, religion, color, national origin, or other criteria in ways contrary to the unity of the nation and the well-being of the state of Idaho and its citizens.