OK, to cover some of the ground in the other topics (but get it right thanks to Nitrogen) here is the last page of Ch.49:
Manga Fox: Kodomo no Jikan Vol.07 Ch.049 Online Manga Scans
In the two balloons Rin says "the only one I love is YOU Sensei."
私が 好きなのは = watashi-ga suki nano-ha
先生 だけだつ = sensei dakeda
She is using "suki" 好き which most often gets translated as "to like." -Ga is an intensifier, and the final tsu つ means she is using a cut-off, emphatic sounding way of talking.
Love can be "ai" = 愛 which (according to this manga) seems to imply requited love or family love, and it can also be "koi" 恋, both kanji include the "heart" character 心.
After Rin's father visits the house and Aoki says to let her choose between Reiji and her father, as he is leaving she says "I love you so much." In the original she says だいすき "Daisuki" -- Nitrogen pointed out that the word "daisuki" (big like = love) is simply being spelled out here and this is really the equivalent of 大好き. Sensei is "spelled out" at least half the time, when the children say it especially.
http://www.mangafox.com/manga/kodomo...5/c035/25.html
The first time Rin says "I love you" is Vol 1, near the end of period 3.
http://www.mangafox.com/manga/kodomo...1/c003/23.html
"大好き だよ" -- daisuki dayo.
And THIS is interesting. In DVD Special 2, Rin-in-disguise says "the children love you (daisuki) -- be sure to love them back (ai!!)"
http://www.mangafox.com/manga/kodomo...c049.1/14.html