According to Vedic system there is restriction that boys and girls should not freely mix, the brahmacaris are strictly prohibited to talk with young women, but in the Western countries this rule is not valid. As such, we have to accept both boys and girls in the same standard. But if each of us follow the regulative principles and chanting of the mantras hardly there will be any chance for sex indulgence. So we have to be little careful about it and Krsna will help us.
Letter to Upendra, 24 June, 1970