There is nothing at all wrong with the Holy Rosary. In fact, it is the most beautiful and rich in graces of all prayers except for the Holy Mass and Our Lord’s Prayer. Here are some saint quotes on the Rosary:
‘If you say the Rosary faithfully until death, I do assure you that, in spite of the gravity of your sins “you shall receive a never-fading crown of glory.” Even if you are on the brink of damnation, even if you have one foot in hell, even if you have sold your soul to the devil as sorcerers do who practice black magic, and even if you are a heretic as obstinate as a devil, sooner or later you will be converted and will amend your life and save your soul, if - and mark well what I say - if you say the Rosary devoutly every day until death for the purpose of knowing the truth and obtaining contrition and pardon for your sins.’
–St. Louis Marie de Montfort
“The holy Rosary is a powerful weapon. Use it with confidence and you’ll be amazed at the results.”
–St. Josemaria Escriva’
“The Rosary is the ‘weapon’ for these times.”
–Saint Padre Pio
“Give me an army saying the Rosary and I will conquer the world.”
–Saint Pope Pius IX
“The Rosary is the most beautiful and richest of all prayers to the Mediatrix of all grace; it is the prayer that touches most the heart of the Mother of God. Say it each day.”
–Pope Saint Pius X
“The Holy Rosary is the storehouse of countless blessings.”
–Blessed Alan de la Roche
“There is no problem, I tell you, no matter how difficult it is, that we cannot solve by the prayer of the Holy Rosary.”
–Sister Lucia, of the seers of Fatima
Also, Our lady gave 15 Promises to those who pray the Rosary:
ourladyswarriors.org/prayer/15promise.htm
So in short, I see absolutely nothing wrong with a Catholic school making the students to pray the Rosary. It is an amazing prayer. I know Our Lady has brought me many graces through praying the Rosary.