The US Constitution's First Amendment protects the right to freely exercise one's religious beliefs, which the parents argued includes the right to pull their children out of lessons they find offensive.
They also pointed to school rules that allow parents to opt older children out of sex education.
Same old debate of establishing 1st amendment. Indian constitution has also borrowed it from America's and I feel that Indians are using it without much of problems even though India is a land of variety. Yes, clashes used to happen here but that weren't about denying anyone's religious rights or any other rights. Most often they were political and personal.