Here in America (California, at least) the courts have ruled that parents do not have a right to limit such indoctrination or query. The US Supreme Court refused their appeal.
Complete control over what is taught (11-28-05)
The 9th U.S. Circuit Court of Appeals in San Francisco recently issued a wake-up call to parents in the case of Fields v. Palmdale School District. Judge Stephen Reinhardt, writing for the court, ruled that though parents have a fundamental right to decide whether to send their child to a public school, they do not have a general right to direct how the school teaches their child. The case before the court that led to this ruling centered on a survey that asked several public schoolchildren invasive questions about sex. The parents argued that the school should not have allowed their children to be asked these questions. The parents, however, had given their consent by signing a form that included the following statement provided by the school district: "I understand answering questions may make my child feel uncomfortable. If this occurs, then ... the research study coordinator, will assist us in locating a therapist for further psychological help if necessary."