I still go to my old high school's (soccer? baseball?) games to support my former junior teammates.
Even though I've graduated, I still go to high school games to cheer on my former junior teammates.
「高校時代（に所属）の部活の試合（後輩の）を応援に行った。」＝ I still go to my old high school's (soccer? baseball?) games to support my former junior teammates. / Even though I've graduated, I still go to high school games to cheer on my former junior teammates.
ボキャブラリー
still ＝ まだ、今でも
old high school ＝ 母校
game ＝ 試合
to support/cheer on ＝ 応援する
former ＝ 前の
junior teammates ＝ 後輩、年下のチームメート
even though ＝ ～なのに
graduated ＝ 卒業した
イギリス 
