Spring break 9 nights suggestions

When you arrive, hop on train to Sevilla, spend X days and return to Madrid for the rest.
You can visit Cordoba as a day trip, but it is not a terrible idea to stop there first if you do not mind one-night stays.
Make a list of what you want to see/do in each place (ideally, make the teen contribute, though they may use Tiktok and not a guide book) and allot days accordingly, easy peasy!

I loved Sevilla and really loved Cordoba. The high speed train to Sevilla from Madrid airport is expensive, but , in general I wouldn't purchase the ticket in advance since air travel can be unpredictable. The last minute high speed train ticket to Cordoba will be cheaper, because its closer.. So, I'd go to Cordoba first. It is a charming city with plenty to do. I'd stay 2 nights (more would be nice, but you don't have a lot of time). Then I'd do the train to Sevilla. I'd recommend at least 4 nights, better 5. Then, return to Madrid. Madrid is a lovely, high energy city, but IMO, doesn't even come close to Cordoba or Sevilla in charm or history. If you were to do this strategy, you could buy the train tickets for Cordoba to Sevilla, and Sevilla to Madrid in advance.

Enjoy your trip. I really love Spain.

I'd fly into Madrid and fly home from Sevilla, with a connection in Madrid--all on the same tickets.

Suggest that you plan an taking in Madrid, Segovia, Toledo, Cordoba and Seville.
Madrid, do a tour of the city that includes the Royal Palace. Consider doing the Prado Art Museum.
Do day trips from Madrid to Toledo and Segovia.
Then head south stopping for the day in Cordoba, perhaps spending one night there.
Then finish in Seville. If you have to fly out of Madrid, then do your final night in Madrid before your flight.

I would do 1 night in Madrid (arrival), a stop in Cordoba, 4 nights in Sevilla and 4 nights in Madrid (departure).
But, whilst Andalucia is certainly the best part of Spain, you might consider visiting it on a different trip when you have more time.
In which case 2 nights in Madrid, 3 nights in Salamanca (Spain's most beautiful city), 2 nights in Segovia (lots to see) and 2 nights back in Madrid.
If you only want two hotel stops, I'd pick Madrid and Salamanca.

I don't know the exact dates of your trip. Southern Spain is likely to have nice, mild weather during your travel period. (It begins to get unpleasantly hot in May.) However, if you run into Semana Santa (Holy Week), you will encounter elevated hotel rates, at least in Seville. I'd do a bit of research on booking.com right away to see what the rates would look like at the beginning of our trip and the end of the trip. There could be a large difference. In addition, cancelation rules can be a lot stricter than usual for Semana Santa bookings. Hotel rates aside, I agree that if you must fly home from Madrid, it's smart to make it your last stop.

Definitely look into open jaw (multi city) airfare so you don’t have to backtrack to Madrid. Such as fly into Madrid and home from Seville.

If you can, take the train directly to Cordova once you land in Madrid. Then spend 2 nights in Cordova, 2 nights in Granada, and 5 nights in Seville. These are the Crown Jewels of Andalusia!

If you can’t do open jaw for some reason, then spend 4 nights in Seville and your last night in Madrid.

LOL! I saw “spring break” in the title and thought, “Oh no, I’m not encouraging a bunch of drunk teens making a mess at our place—they should stay there and head to Florida!”

Although we do have our own “teen problems,” thankfully, it’s not on the scale of US college spring breaks (I’ve lived through more than one when I was in the States :). In Spain, it’s not really tolerated, and most people frown on it. That’s why it’s mostly restricted to specific touristy spots, like Lloret in Catalonia, Magaluf in the Balearic Islands, Benidorm or Maspalomas in the Canaries, and mostly by visitors. Locally, we have what are called botellots in Catalan (or botellones in Spanish), where teens gather in parks or on beaches, make noise, and annoy the neighbours. But the police crack down on it.

Anyway, back on topic… since this isn’t one of those crazy spring breaks, I’ll go ahead and give some suggestions :) Yet, without knowing exactly your teen’s age or interests, it’s tricky, but a few ideas come to mind that might appeal:

In Madrid, you could try rowing boats in Retiro Park for a classic, relaxing experience, or, if he/she's into football (yeah, I refuse to call it soccer, sorry... ours it's kicking a ball with the feet, so foot-ball), a tour of Santiago Bernabéu Stadium to check out the stadium and trophy room. A street art tour in Malasaña is also fun, exploring colourful murals, graffiti, and quirky boutiques, which are super Instagrammable and full of local character. Of course, grabbing churros at San Ginés is a must, especially with a big cup of chocolate for dipping. For something more hands-on, Matadero Madrid offers contemporary exhibitions, live performances, and interactive workshops. There are also plenty of escape rooms or VR experiences around the city for teens who love puzzles and gaming. For a more relaxed vibe, rooftop views at places like Azotea del Círculo or The Hat Rooftop give great city panoramas without feeling too touristy.

In Seville, renting bikes and riding along the Guadalquivir River is a fun way to explore, or taking a horse carriage ride around the historic city centre adds charm. You could also check out a flamenco show with an interactive workshop, where some places let teens try the basic steps or rhythms, which makes it both fun and memorable.

You have so many good answers and it makes me smile to think about planning a trip like this. My first trip to Spain was with my daughter (who was a first year teacher) during her spring break. (Spring break in March, not April)

I agree that multi-city is often wonderful. But flight times didn’t work for me - so it wasn’t helpful. Plus cost (in this case) was somewhat significantly higher. So…. if you need round trip Madrid, I might look at Nick’s suggestion of Madrid and Salamanca (fitting in Segovia and Toledo somehow) - or if heading to Andalusia, maybe head from the airport to Cordoba for 1 night (this always feels like a better use of my arrival day for some reason), then Seville (4), Granada (3), and back to Madrid (1).

The latter means not much time in Madrid. And that depends on what you enjoy. Madrid is growing on me, but I still love all the other cities more. lol. There really isn’t a wrong choice, though.