As someone new to the MMO scene, I have been a Star Wars fan since the first film in 1977. This game builds more on the Knights of the Old Republic games that came out several years ago, only now we have the advantage of much more immersive storylines (the originals still stand as pillars to the genre), better graphics and multiplayer options. Star Wars itself has both a very black/white nature when it comes to morality, but as with anything else there are details that add to the narrative that make it more of a learning experience and understanding the characters. I basically have a few key points:
1) Violence. If your kid has never seen the prequels, never seen limbs and arms sliced off with lightsabers, this is in some cases less graphically violent than the films. There is, however, a LOT of violence in general, because the story involves both active and passive elements of a war spanning the Empire and Republic across the galaxy. Armies clash, specialists are sent in on missions with violent or peaceful outcomes, and it all depends on the multi-layered choices the player makes. You start out with 3 choices in most dialogs: Good, Neutral, and Aggressive/snarky. The choices descend from there, and you get light or dark points based on the outcome. Therefore as others have said, you can play as a dark Jedi or a Good Sith, and the outcomes are still very interesting. There are choices in encounters that involve no violence at all for a Sith, but require a Jedi to kill. So, consider that - like life - there are consequences for your choices and actions, there are many outcomes.
I would also add that your relative light/dark score affects the appearance of your character and - most importantly - whether the character can use cool gear which has a light/dark score prerequisite.
2) Sex/swearing/bad habits: There were scantily-clad stripper/dancing girls in Return of the Jedi. This is the same except that there are more dance clubs. Red light districts of a sort are on almost every planet, and cantinas are a neutral zone of sorts, so you're going to get involved. One of your first missions as a Jedi is to "rescue" a despondent boyfriend's Twilek girlfriend from her dancing job, and the outcomes don't involve sex at all, but may involve her remaining an exotic dancer because it's her choice. A Jedi can force her to leave, earning dark points or allow her to decide for herself and telling the boyfriend she honestly doesn't love him anymore, earning light points. I have two boys and both saw this mission as nothing erotic or suggestive. There is a very limited amount of swearing, and many of the lounges do offer the character options to buy drinks, but these are mostly backgrounds in the scene. Drugs are involved in some missions, but involve medicines to be rationed during the war, and deciding whether to give them to injured soldiers or to widows and orphans. Again, both decisions the player has to make and both with different outcomes depending on the ROLE PLAY, and that's part of the "RP" in "RPG". If you have an imaginative child, they can run a character as a juggernaut of death or a beacon of light, and it's interesting to see how or why they do so. Watch and learn from their styles in different gameplay.
I would also add that much with the movies, almost ALL kids liked the bad guys. Stores didn't sell out of Jedi costumes and toys, they sold out of everything Darth Maul/Vader-related because bad = cool. Apply the same mode of thinking to monster trucks of professional wrestling. The one thing this game does offer in terms of sexual politics is the women have as much influence as the men in the galaxy as a whole, and female characters or companions can have interesting, complex back stories that define who and why they do what they do, and how they change based on your companionship. The one thing I cringed at was the Sith "punish" ability, which let you slap a companion as a simple visual device. You earn no points for it, but the female companion will cry and turn away, but the gigantic, Jedi-eating alien with snivel and whimper like the cowardly lion. However, in other character classes you can kick enemies in the groin or backhand them across the face with your blaster/rifle as a form of attack, so again, if this type of violence - which they are apt to see in any TV show on in prime time, and in many cases TV is worse - is immediately prohibitive or offensive to a reading parent, then stop here and don't allow the game for your kids, but it's a minor issue on the whole.
3) Consumerism. This more than any other aspect of the game is your caveat emptor. It is free-to-play, but as with any other similar MMORPG, this limits how far you can advance, who you can play with and what gear you can use based on paid subscribers. The fees aren't outrageous for the basic subscription, but the Cartel Market (CM), the player's "Christmas Toy catalog", is a huge money sink (and I say this as both a parent and someone who keeps feeding the monster) because it DOES get you cool gear, outfits, vehicles and other perks. Your kid gets 500 coins with each monthly subscription rotation, which allows them to buy maybe 10% of the available items in the CM.
You can buy cartel coin packs on the game website for cash, and a $40 investment gets you about 5,500 coins - enough to buy ONE big ticket item or dozens of smaller ones on the market. The big thing to learn with your child if you go down this path is the "Collections" feature, which allows you to purchase CM items for all characters on the account for a fraction of the original cost, thereby allowing your entire span of players access to the gear. Dressing a Sith as a Smuggler sounds corny, but it can work. There are many guides on YT and the various SWTOR sites (I would recommend Dulfy.net as a good starting point) on how to do this economically so you don't max out a credit card.
I would also add that it teaches your child VERY quickly the value of something - if they make a rash judgment in a purchase that takes all their coins AND they equip their character with it, it's forever bound to that character until they add more coins to add the outfit to their account collection OR and this is the big economics seller for this game, they can choose NOT to use the item and sell it on the GTN - the player's auction board (Galactic Trade Network). Any player can go to these kiosks and look to see what their purchased gear is selling for across the board, can purchase gear and mods they haven't learned yet, and can earn a huge amount of in-game credits from something they paid $10 for on the CM because it's a rare drop. Again, these are all common to MMO players but it teaches your child the economics side of things. But money does make this game operate and you can spend ridiculous amounts with it.
4) Miscellaneous. I saw on here two primary issues with the game - the sexuality of the cutscenes and the safety/privacy concerns. Sexuality as indicated is a minor element, offscreen, but adults will likely catch subtle clues in the gameplay, which is actually enjoyable for them (one of the companions is a dark-side turned Jedi Padawan who just LOVES being evil - her voice acting during the romantic cutscenes is so cringingly bad that it seems like a bad soap opera); romance and intimacy is poorly-written by Lucas and Co., and it shows to some degree in-game.
The other aspect are safety/privacy. Any character your child creates can join a guild if invited, and General chat is mostly full of credit/cartel coin spam with embedded links, so lock your browsers down if you need to - again, monitor their gameplay. Safety can be augmented in the Preferences | Social Menu, but it has to be toggled for every character on the child's account, so some parental involvement is recommended.
My best recommendation (and to some, this may sound like a scathing review but I still love the game and recommend it as a whole) is to get involved with your child. Group missions can be a blast, and with only 4 accounts and 5,000 credits, anyone can create a guild which offers some impressive experience and credit bonuses. I play Skype with my two boys and their friend (their group audio/video chat is now free for anyone with a Skype or Microsoft account) and it's totally worth it. There are many sites out there to recommend guilds if your teen wants to join (most teens will have heard the language in Skype/vent/teamspeak - or worse - from schoolmates by that time), but I would recommend keeping the social aspect limited. Any player can play through the entire game without one bit of social play, but unless your child is insistent on planetary or class achievements, socialization is a requisite, as some can only be done with group mission completions.
The gameplay and grinding can get boring, and cutscenes tend to be repetitive but you can push through all of them. Overall I found it a decent Star Wars game but pretty consistent as far as other MMOs tend to go. I've played Warcraft and Everquest in the past but not in the same degree as this game, but friends I know into MMOs at an advanced level only disliked it for the simplicity of completion and gross consumerism as I indicated above.