Who does or doesn't count in a minyan (quorum of ten) is a most controversial topic. First, we must decide if the concept of "minyan" is Biblical or Rabbinic. The rule is that in case of doubt, we must be stringent with a Biblical law, but we may be lenient with a rabbinic law. The Talmud derives the requirement of ten from the story of the spies. Twelve men were sent to spy out the Land; two brought back a good report, while ten brought back a bad report. G-d tells Moses and Aaron "Separate yourselves from this evil congregation". We thus learn that a "congregation" is ten. But is this a principle derived from the verse, and hence Biblical, or a rabbinic concept, that was "leaned" on to the verse (asmachta)?The view of the majority of authorities is that the principle is rabbinic, allowing leeway for some flexibility. The conclusion of discussions in the Talmud on this topic, clearly state that only adult (over thirteen) males can count towards the requisite number of ten. There is, however, an opinion that the Ark, containing a Torah scroll,can be counted. This view is rejected. However, in many times and places, this view was relied upon in emergency situations. Rabbenu Simchah, the author of Machzor Vitry (a student of RASHI, d. 1105) opined that in case of need, a minor, a woman, or a Torah scroll could be counted as the the tenth "man". However, about a century later, Rabbenu Tam, the greatest of the Tosafists, refused to consider this view whatsoever. A somewhat later authority, Rabbi Mordechai ben Hillel (1250–1298), quotes Rabbenu Simchah's view, wondering if it must be limited to one child, scroll, or woman, or even several, as long as there is a clear majority of adult men. Practices varied. The author of the Shulhan Aruch, Rabbi Yosef Karo, totally rejects these ideas, including only adult men in a minyan. Rabbi Moshe Isserles (RAMA), the major Ashkenazi voice in the Shulhan Arusch, reports that the widespread Ashkenazi custom was to allow a boy, over six years of age, to hold a Humash (text of the five Books of the Torah), and count him as the tenth man. This view is based on the concept of "Tziruf"; combining two rejected, minority opinions, as a positive. (The Vilna Gaon consistently fought this approach). The vast majority of later rabbinic opinion rejected this liberal view, yet it persisted in many places. The turn of the twentieth century legal code, known as Mishnah Berurah, rejected the counting of a child, which sounded the death knell for he practice in "Yeshivish" circles. The practice still continues in many Hasidic circles, as well as some non Hasidic. It was commonly followed in many American congregations. I have seen non Orthodox synagogues count the Torah scrolls in the Ark towards a minyan, but I have never seen that in an Orthodox synagogue (although this practice can be justified based on the Talmudic opinion to this effect, combined with the view of Rabbenu Simchah that this may be relied upon in an emergency). Rabbi Moshe Feinstein opined that only in case of the greatest emergency, such as a synagogue in a dying community that no longer has a regular minyan, can a child, WITHIN A YEAR OF BAR MITZVAH, be counted while holding a Torah Scroll (NOT a printed Humash), for the purpose of reciting Kaddish, Kedushah, and Barchu, but not saying any extra blessings, such as the reader's repetition of the 'amidah. Non Lithuanian Ashkenazim continue, in many places, to rely on the child alone (without Humash), conducting a full service. Israeli Sepharadic rabbis have condemned the practice, but it is accepted by some American Sepharadic rabbis. This issue has not yet been resolved. Each side has valid arguments. Like many other issues, it awaits the ruling of a Sanhedrin.