Teaching how to take a hit

Work some drills on the dummies, keep after him, be patient. Once the light bulb goes off and he discovers how to gain a leverage advantage and what happens when he runs through contact the light bulb will go off. If not there is always track.

to teach collisions, you have to break it down into small steps. 1st get them close to each other, fit up and drive. When that is accomplished, move to just having them face to face and then fit and drive. From that, move to a stance (even a FS can get in a 3 point or just have both in a 2 point -- both have to be the same) get off the ball, fit and drive. Then move the 2 players back from each other. As you move to each step, make sure to emphasize pad level and leverage.

correct along the way and regress (from the progression above0 if needed.

the biggest mistake that coaches make is to think young pups will just run in there and hit something. It just isn't logical for human beings to do that. Plus, boys are not allowed to be 'physical' in school (recess, PE, play ground) so that they have no frame of reference for using their size and doing what most of us have just done since we were kids -- rough housing.

Youth coaches deal with this all the time. These are just some ideas on the subject.

First of all, define the problem: A.) Is he shying away from contact? Or, B.) Is he using incorrect technique when making contact? i.e.... running straight up, hitting with head down, arm tackler, etc...

If he's shying away from contact, it's a confidence problem. I'd start with what coachwoodall posted. You can also add in having the players get on their knees and tackle from there. That will help with form, fit & hip explosion. Progress to a standing position and then, eventually to placing tackle dummies behind the hittee while the hitter tackles him to the ground. Hitter shouldn't have to be more than 1yrd away.
Sumo drills will help teach him to be physical.

If the player is using incorrect technique- in this case- making contact with his body in a straight-up position, I'd let him practice at getting his shoulders lowered and head up until it became a muscle memory thing with him.
Whether he's offense or defense; never tell him that he's learning to take a hit. He's always learning to deliver the hit. You want him to learn to use a 'half-man' technique when hitting through the defender. Don't allow him to hit dead center. Teach him to lower his shoulder pad and strike either the left or right chestplate (half of the man) of anyone trying to tackle him.

In these cases, gauntlet drills with players in two rows hitting him with handshields and tackle dummies will usually get him to improve. He won't be able to make it through without lowering his shoulders and keeping his head up. If he's knocked down, make sure that his teammates let him back up before going at him again.

There are receiver drills that mimic this, also. WR catches ball. Someone with handshield hits him immediately after catching the ball. You can use this, too. Just back the player with the handshield off a few yards. Let your shy TE catch the ball, turn, take about 3 steps before delivering a shoulder strike (half-man) into the player with the handshield.

RB drills that make the runner break through the line are helpful.

As for defense, defense requires all of the above plus one added element- aggression. It's a little harder- but, far from impossible- to teach aggression. Defensively speaking, I tend to place good, fast technical tacklers(not necessarily hard hitters) at CB. I place good, fast and aggressive tacklers (hard hitters) at Safety.

You know the player better than I ever will. But, it sort of sounds like he's more of a RB/CB than a TE/FS.

EDIT: OOPS! Almost forgot. Teach the he!! out of blocking. Blocking is hitting! O-line block drills, RB block drills, WR stalk block drills....whatever. Make him very good at whichever ones you want him to learn. There are way more blocks and attempts to defeat blocks per game than there are tackles. Emphasize blocking.
Personally, I'd go with RB block drills & WR stalk/open-field block drills. You will see a world of difference in his game play once he is a confident blocker!

TO me there is a spectrum:

20% of kids are born ready to hit
50% of the kids can be taught to hit
10% of the kids will never like to hit
20% are too afraid to turn out for football!

Our job as coaches is:

1. To keep the kids who like to hit healthy and not intimidate the middle 50%.
2. Train that middle 50% how to hit.
3. Not let that bottom 10% suck up any of our valuable time.

Keys for training the middle 50%:

- Good technique
- Start close and slow and build from there
- Positive encouragment
- Treat kids as individuals in regards to contact