Answer:
According to the teaching of the Catholic Church, yes. Some other sources disagree. Assuming that you believe in sin at all, a reasonable answer might be yes, if done intentionally. If you got them into trouble or got them hurt than definitely yes.
According to the Bible also yes.
Would God dissaprove... Yes therefore if intentional then its a sin
Biblically:
Matthew 18:6. 7 - But whoever causes one of these little ones who believe in Me to sin, it would be better for him if a millstone were hung around his neck, and he were drowned in the depth of the sea. Woe to the world because of offenses! For offenses must come, but woe to that man by whom the offense comes! [NKJV]