“So, in your Protestant sunday school classes you just hand the kids the Bible and walk out of the room?”
Usually, the study consists of reading and studying the scripture. We recommend everyone read the Bible on their own, and frequently, when not formally going over lessons in church.
In theory, the RCC should be able to do the same, and teach all of its doctrines from it, without having to resort to snippets of catechism that in no way helps a person understand the full meaning of a particular book or epistle. I tend to find Catholic teaching to be... choppy. I can’t explain it any other way.
2Ti 3:16-17 All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: (17) That the man of God may be perfect, throughly furnished unto all good works.
Of course, in truth, it’s impossible to even come to any understanding of the scripture at all unless one is regenerated in the first place, which is a sovereign act of God.
1Co 2:12-13 Now we have received, not the spirit of the world, but the spirit which is of God; that we might know the things that are freely given to us of God. (13) Which things also we speak, not in the words which man’s wisdom teacheth, but which the Holy Ghost teacheth; comparing spiritual things with spiritual.
No matter how good the lesson by man, it is the Holy Spirit who is the only real teacher.
"Understanding this first, that no prophecy of scripture is made by private interpretation. For prophecy came not by the will of man at any time: but the holy men of God spoke, inspired by the Holy Ghost." 2 Peter 1:20-21
"And account the longsuffering of our Lord, salvation; as also our most dear brother Paul, according to the wisdom given him, hath written to you: As also in all his epistles, speaking in them of these things; in which are certain things hard to be understood, which the unlearned and unstable wrest, as they do also the other scriptures, to their own destruction." 2 Peter 3:15-16