@panzerkaizer no I think last year of middle school ie 14 or 15
They're both still in the second year of middle school at this time. It's that pick-up artist senpai that tries to get with Yamada that is in the last year of middle school. This will be spelled out when we get to the closing ceremonies in a few months from this chapter, and they transition into third years at that time (the story should currently be in third year as of current real-world date and latest chapters, but that's besides the point for this chapter in question).
To be specific, Ichikawa (Kyo) is currently 13 (his birthday is at the very end of the Japanese school year, right around the start of spring break), and Yamada is 14 (she was born around the shift between summer and autumn).
The story hasn't even passed a single actual year in-narrative. Ignore all the extras that have shown us multiples of various holidays- they don't count as those were drawn for the real-world date passing by, not the in-manga date.