If you participate in a wedding or funeral not of your belief, you are acting out of respect and not stealing a benefit to which you are not entitled by deception.
UK faith schools "may give priority to applicants who are of the faith of the school",[1] but must admit other applicants if they cannot fill all of their places and must ensure that their admission arrangements comply with the School Admissions Code.

That is why atheists lie and cheat to get a faith education for their kids even if it may deprive genuine Christian's of a place at a Christian school.