"I have heard it said that if parents, etc. do not raise their children, teach their students correctly, then many children, students will end up in Hell. I don't believe this. I think that because of our free will that each of us will have the opportunity to decide where we want to go."
There are many incorrect beliefs about the Catholic teaching on Hell, and many of them circulate even among fairly well-educated Catholics. One of them is articulated and repudiated above, specifically the belief that we are held eternally responsible for the sins of others.
It is true that in our free will we each have the opportunity to decide where we want to go, and even to decide where we will actually end up. The Catechism makes this clear in more than one place, just as Jesus did in the Gospels.
What does the Catechism tell us, based on Jesus' teachings in the Gospel, about how we will be judged?
"1039 In the presence of Christ, who is Truth itself, the truth of each man's relationship with God will be laid bare. The Last Judgment will reveal even to its furthest consequences the good each person has done or failed to do during his earthly life:
All that the wicked do is recorded, and they do not know. When 'our God comes, he does not keep silence.'. . . he will turn towards those at his left hand: . . . 'I placed my poor little ones on earth for you. I as their head was seated in heaven at the right hand of my Father - but on earth my members were suffering, my members on earth were in need. If you gave anything to my members, what you gave would reach their Head. Would that you had known that my little ones were in need when I placed them on earth for you and appointed them your stewards to bring your good works into my treasury. But you have placed nothing in their hands; therefore you have found nothing in my presence.' "
The Catechism quotes St. Augustine's paraphrase of the Gospel here, and we can draw something important out of it to answer the question posed initially. Notice that Augustine's paraphrase of the Gospel ends by emphasizing that when we place nothing in the hands of those to whom we have a responsibility for loving Christian kindness, we find nothing in the presence of God.
In principle, this points to the fact that if we fail to do our part to draw people to receive Christ who is the Bread of Life, the most important and substantial something we can place in their hands, then we will be held responsible for our failure to do so. In the same way, parents and catechists and religious brothers and religious sisters and priests and bishops and the Pope will be held responsible if they fail to draw people to receive Jesus, if they fail to help them encounter the greatest gift of all.
Because "man does not live on bread alone", the command to "feed my lambs" is not merely a command to multiply the loaves and fishes so that the poor and vulnerable can have full stomachs; it is also a command to help them to find the Bread of Life provided to us by God. Of course, if we love Jesus, then we will keep His commandments as he said that we would, and part of that is to go and make disciples of all the nations.
We would be best served to do this not because we are afraid that others will go to Hell because of our negligence, or even because we are afraid that we will send ourselves to Hell because of our negligence (which is a real possibility), but because we sincerely want to keep the commandments of the one who loved us unto death so that we need not be afraid of that death any longer, the one who showed us the path to Heaven so that we need not be afraid of Hell.