I can't help but agree to the statement that \"a person is the average of the 5 closest person he/she hangs around with\". This applies to personality traits, mindsets, risk appetites, hobbies and interests, and more than not - the shared values. When a kid gets introduced to school, he/she enters a stage where the environment they are in; the peers and elders they interact with, start to mold their value perception.

Here's a quick runthrough of the Freudian theory relating to the pleasure principle, which I'm going to build on in the later part of the post:
Freud's Tripartite Personality Theory explains that the human psyche consists of 3 major aspects, the Id, Ego, and the Superego. The Id is the primitive component of personality that is present in humans when they are born, consisting of the life instinct (sex and propagation) and the death instinct (fight for survival, aggression). The Id is instinctive and exists in the unconscious mind, constantly making demands and desires regardless of the external world. When a desire is satisfied, the Id will derive pleasure. It is often regarded as the selfish and fanatical part of the personality.
Building onto the Id is the Ego, which is molded via the environment, and serves and the mediator between the unrealistic Id and the real world. It helps the Id develop a realistic way to derive pleasure.
Then comes the Superego, which starts developing on the age of 3-5. This is the part which incorporates societal values, builds personal consciences, and controls the Id's impulses.
So, imagine an iceberg of personality - a good man will get born with the Id, with the Ego and Superego building up as one ages, and it develops according to their interaction with the real world. The education of values to a 3-5 year old kid is like writing on a clean slate. This is also the most important point of time to educate your kid about values. As your child grows, any additional morals and values will be built upon the existing superego, and values that were ingrained in the kid when they were younger will be reinforced. Just like the melting of an iceberg, if your child were to shred a trait, it will also be the ones that are more recently acquired.
When your child reaches ages 10 and above, inculcating values into them will begin to feel like firing Nerf guns at a boulder, some of which may build up and be lost almost instantaneously, some of which might even be immediately dismissed as being \"lame\" or \"old-fashioned thinking\"; which yes - can be very discouraging for you. This, ironically, is also approximately the age of puberty. To them, much of their bandwidth is already spent on navigating their confusing stage of life, and there's really no additional bandwidth for new values or way of life. Yes, biological and psychological development do work parallel with each other (in this case), but they do not work in favor for parents during the puberty stage as kids enter the phase of rebellion.

TL;DR
In summary, when your child is approximately 3-5 years of age, it can be a really tiring time for you as they are at the most curious of their minds (\"why\" will be their favourite word). However, it is also the most crucial 2 years for you to perform for your child's future moral-bearing and well-being. If a parent were to be role models and set good examples - this is the crucial time. They may seem playful and too immature for their age to take in some of the more abstract values you may want to educate them on; but why not let them surprise you in the future?
As I've mentioned earlier in my post, the environmental factors are pivotal in the development of the values of a kid. Therefore, it is of utmost importance to send your children to the most trusted of trusted early education schools, where they provide a conducive environment for great morals and values to flourish. So, when you ask your children what they've learnt at school today, encourage them to share about the life lessons they've learnt instead of the academic side. Simple tip, for your kid's future, even if you're not High SES, it might be worth it to break your bank a little bit for a better early education.
As your child grows into a teenager, our role as parents switch from an educator to a beacon of light. They are no longer reliant on you for survival and you have to recognise that. They do, however, turn back to you when they start to lose their track. So all in all, do be there when they need you, but it will no longer be the time where you can impart values to them. Continue to do what you're comfortable with, but please do not expect your child to be able to accept all of your preaching.
Back to the first statement I've made - a person is the average of the 5 closest person he/she hangs around with. However, they gravitate towards people with similar fundamental beliefs. As with my analogy of the personality iceberg, people with similar core of the iceberg get along well together, whilst the surface of the iceberg get molded by those people you get along with. As much as you don't always hang out with the same 5 people in your life, the surface of your personality always changes, but the core of the person always remains uniquely theirs.

Thank you for reading and hope that this might be of help to some people out there

(This piece might not be applicable to children with special needs)