I do not know if you friend would make this argument, but when I have heard people express this concern in the past, it has usually been based on the assumption that a boy becomes a man, when he becomes a Christian. Since women are forbidden to teach over a man (
Titus 2:3-5; I Timothy 2:13-15), women are therefore forbidden from teaching young boys, who have become Christians - or, so a person might argue.
I am unaware of any restriction for women to teach boys. In fact, women are to be
"homemakers", and they are to
"manage the house", which would include any children (
Titus 2:3-5; I Timothy 2:13-15). Unless one reaons that boys become "men" by choosing to become a Christian, I do not know how one could remotely forbid women teaching boys.
Assuming this is the argument being made, it is true that women are not
"to teach or to have authority over a man" (
I Timothy 2:11-12). However, who said that boys become men, when they become a Christian?
I believe the Bible indicates that it would be unreasonable to consider these boys as men:
- Men are to earn a living and provide for their family (I Timothy 5:8). Are these boys independent? Supporting at least themselves, maybe a family?
- Women are to be in submission to men (I Timothy 2:11-15), and Paul's command expresses that. Do you obey these "men"? Or, do they submit to you? If they are indeed "men", then you have no authority to command them in anything, because the rule was established in creation, not culture or any other limited scope. If they are too young to take up this responsibility, then they are not "men".
Now regarding your question regarding your own boys, please consider these verses:
- Ephesians 6:1 - Children are to obey their parents. This implies some authority to command and rule, which is granted to mothers and fathers ("parents") and extends to sons and daughters ("children").
- Deuteronomy 21:18-20 - Fathers and mothers were instructed to bring rebellious sons before the council to be stoned. Were these little boys? No, they were mature, responsible sons, guilty of mature sins: "stubbornness", "rebellion", "gluttony", and "drunkeness". Notice that part of the cause for execution was the son's failure to obey his mother's voice. Granted this was part of the Old Law, but the rule of submission is based in creation. It applies in the old and new covenant. Therefore, if the mother's could command her son under the Old Law and not violate woman's submission to man, then such a command would not violate it under the New Law.
- Proverbs 1:8 - The wise man simply commands sons to obey the law of their mother. Considering the whole book of Proverbs, it would be strange to think these sons as "little boys".
Ultimately, I believe this comes down to a question of defining the age of manhood. Since these are clearly dependent boys, it becomes incumbent upon your friend to justify that they are "men".
If your boys, or someone else's boys, are still in submission to their mothers, I do not see how anyone could Biblically call them "men". Consequently, I would see no restrictions regarding your teaching of these boys.
Regarding your final question, one might could argue that an incidental male observer would not be subject to being "taught over" by a woman teacher. However, such reasoning seems to be dangerously approaching that somewhat fuzzy definition of "teaching over". Therefore, to be safe, I would encourage you to consider pausing and politely asking the man if he would like to teach or say anything. Likely he will decline. I would then possibly express the inapprorpiateness of a woman to teach over a man, but I would certainly dismiss the class for a small recess, possibly expressing your uncomortableness in continuing, if it seems appropriate. This would allow you to further speak privately and discretely with the man, and the pause would allow him to pursue his original business.
As a side note, I consider it
wise for children, especially boys, to have male Bible teachers as they approach adulthood, simply to smooth the transition to adult classes and to provide a good role model for the maturing boys. Therefore, in spite of what I said previously, it may be
better (not necessary) to have a male teacher for this spiritually focused class, especially for the benefit of the 15-year old boy. Certainly, it would be safe, and such a concession might defuse unnecessary conflict.