Child:^[1]

Children do not join a Minyan. However, if there are only 9 people in a Shul and there is a male child present who is of age six and above and knows to whom he is Davening, then some Poskim allow the child to join the Minyan if he holds a Sefer Torah, or Chumash, or even if he does not hold anything in his hand. Practically, the main opinion follows the stringent opinion that a child can never join a Minyan even if he is the 10^th person and holds onto a Sefer Torah in his hand. This applies even in a time of need. Nevertheless, those who are lenient like the former approach are not to be protested as they have upon whom to rely, however, even they should only recite the obligatory Kaddeishim and Barchu on this basis. The Chabad custom, however, is not to rely on this opinion, and hence we do not join a child to a Minyan in any circumstance.

[1] See Admur 55:5; Michaber 55:4; M”B 55:24; Shulchan Menachem 1:65; Piskeiy Teshuvos 55:9