Hi, Ellington parent here. I don't have experience personally with your situation but I talked with a student last year who came in at a French IV level so I have a little bit of info.
Ellington used to offer French IV and AP French but there aren't enough students to fill out those classes these days so they were dropped. Also Spanish IV was not offered last year either. To me it seems chicken and egg-- you don't offer the classes so you don't get the students wanting those classes. But I digress.
This student took French outside of Ellington-- I think online. I don't know if she paid or DCPS paid. She took the AP French exam, which you can do without taking the AP class (a lot of parents don't know this but any student can take an AP exam in any subject without taking the AP class). She also was considering the programs where DCPS kids can take classes at universities --
https://dcps.dc.gov/service/participate-dual-enrollment. I don't know if she ended up doing that or not.
Another way to go would be to take Italian or Spanish instead of French. Ellington offers both.
She can also apply for a DCPS study abroad trip her junior summer to a French speaking country, all expenses paid. Most kids who apply can go as there are a lot of trips and spaces available.
Good luck!