I would ask the teacher who was wrong about Mary. The early reformers agreed with the Catholic teaching of Mary’s Perpetual Virginity. Are they wrong or is the interpretation this group holds wrong. Which of course leads to the obvious ?, if there is differences in views who is going to “decide” who is right without guidance from the Holy Spirit to lead without error in matters of faith and morals? THE PROTESTANT REFORMERS ON MARY
When Fundamentalists study the writings of the “Reformers” (or founders of their particular sect)* on Mary, the Mother of Jesus, they will find that the “Reformers” accepted almost every major Marian doctrine and considered these doctrines to be both scriptural and fundamental to the historic Christian Faith.
**Martin Luther:
**Perpetual Virginity
Again throughout his life Luther held that Mary’s perpetual virginity was an article of faith for all Christians - and interpreted Galatians 4:4 to mean that Christ was “born of a woman” alone.
"It is an article of faith that Mary is Mother of the Lord and still a Virgin."2
John Calvin:
It has been said that John Calvin belonged to the second generation of the Reformers and certainly his theology of double predestination governed his views on Marian and all other Christian doctrine . Although Calvin was not as profuse in his praise of Mary as Martin Luther he did not deny her perpetual virginity. The term he used most commonly in referring to Mary was “Holy Virgin”.
"Elizabeth called Mary Mother of the Lord, because the unity of the person in the two natures of Christ was such that she could have said that the mortal man engendered in the womb of Mary was at the same time the eternal God."7
“Helvidius has shown himself too ignorant, in saying that Mary had several sons, because mention is made in some passages of the brothers of Christ.” Calvin translated “brothers” in this context to mean cousins or relatives.
"It cannot be denied that God in choosing and destining Mary to be the Mother of his Son, granted her the highest honor.
“To this day we cannot enjoy the blessing brought to us in Christ without thinking at the same time of that which God gave as adornment and honour to Mary, in willing her to be the mother of his only-begotten Son.”
*
****“It was given to her what belongs to no creature, that in the flesh she should bring forth the Son of God.”
“I firmly believe that Mary, according to the words of the gospel as a pure Virgin brought forth for us the Son of God and in childbirth and after childbirth forever remained a pure, intact Virgin.”
Zwingli
used Exodus 4:22 to defend the doctrine of Mary’s perpetual virginity.
“I esteem immensely the Mother of God, the ever chaste, immaculate Virgin Mary.”
"Christ … was born of a most undefiled Virgin."Ulrich Zwingli:
“It was fitting that such a holy Son should have a holy Mother.”
“The more the honor and love of Christ increases among men, so much the esteem and honor given to Mary should grow.”
catholicapologetics.info/apologetics/general/mary.htm