I myself went to a Primary and Secondary education in French and learned English as a second language and there are a few things I would like to add! Our Core English class is similar to the first language English in exception that for example, the English we were taught in grade 12 for example argue it is somewhat the same level as grade 11 first language English and somewhat the same as first language English 12 as well! In other words, were at a similar level than first language English and what is funny is that I was only taught English as of grade 5 and up under the old system but lucky for me, already knew English pretty well as a kid and to add things even more, when they changed the start of teaching English from 5 to grade 3 to begin English second language, there was reports we would of been behind since in grade 7 and 8 and higher changed the level to harder and was meant for grade 3 to 12 and not 5-12, however, we did it like a boss and did as well as if we started in grade 3 and some reports even shows we did better than the ones who start in grade 3! I forgot to add that we also have 2 different English levels and the easier one is meant towards the ones in the old 5-12 grade system and or the people who are weak in English similar to core French but the harder Level is meant for people who are intermediate plus, advanced and superior! I myself was advanced at the time in grade 10 when I was scored but would now be considered Superior if retested since at the time, i had a much thicker accent and can now pass as either french or English as long as if i spoke English, I would change my accent a bit and losing the thick accent in English which I was able to do thanks to college! The harder English was meant to be at similar levels than first language English which it was since we were taught shakespear, some pre university level projects in grade 12 and of course practice our English!
Now as for french, i heard core french is not even close to our french while french immersion is similar or if you were a 80s-90s kid actually harder than first language french! My french was hard since it was a first language but it was a very good advantage for me to learn it and I was born as a French and English Mother tongue since i was taught both at a similar age, however, i may have a slightly bigger back ground in french but i am slightly stronger in English which is weird! The only thing I wish was that in grade 9, I could of went to an English High School to improve my English and could of helped me for Math and Science since I did struggle in French from grade 8 and later on as far as for some wording since during around those times, our french was becoming like the France/Quebec level and we were used to the new brunswick french and most were ok in my class but I did struggle since I was more new brunswick/acadien French since my family was Chiac which was a mixed of English and french and or french and or english! I happen to be more chiac, acadien French and English around 8th grade!
I myself believe that we should have a system where french and english should actually be taught both as mother tongues or that if we keep both languages as separate schools we should have a 30-70, 40-60 , 50/50 system and that both english and french are taught!
For example, in french schools, have math as (optional english or french), science, history and french as the french courses, english, physical ed, music, art( as optional french or english), should be english!
In the english system, English, History and Science as english, Math optional English or French, Physical Ed, Music, French for French and Art as an optional English or french course!
If we did the first 2 language mother tongue system, it would be a 50/50 system, however, it would begin with 1-2 english, 3-4 for french, 5-8 50/50 system in exception with Math and Science being offered in english or french, 9-12 an optional english only or french only stream or remain in 50/50 system as same options for math and science for english or french! Just my opinion but i believe the two options would be better than french immersion or french and english core!