Species counterpoint is not "real" counterpoint - it's just a pedagogical system which breaks contrapuntal music down into isolated skills. For those who haven't delved in; in first species for example, you simply write one note against another note, usually in semibreves. In 4th species you have to write semibreves in one part and suspensions in the other. There are strict rules to adhere to.
What you produce is not really "music", because you have to obey so many rules, you cannot be creative. However, in my opinion, it's an excellent way to understand the principles of voice leading, consonance and dissonance, and shaping a melody, which will definitely make writing in a contrapuntal texture easier for you. As long as you understand that the system is purely pedagogical (and fixed at the style of Palestrina, so not even as modern as Bach...) it has its uses. If you want to study Baroque (or later) counterpoint, then it is a good starting point.
In terms of ABRSM theory grades, it will help with writing in 3-part contrapuntal texture required at grade 8 (Baroque trio sonatas), and to a lesser extent it will probably help with Q2 writing in a later keyboard style. None of the grade 7 questions would need any real contrapuntal skills. If you are doing diplomas, it will help with writing Bach-style chorales in the AmusTCL and with writing string quartets in the LmusTCL, but you are not tested on the distinct "species" skills.
It's not fashionable at the moment, as Hildegard mentioned, probably because it is too rigid. Some unis still teach it - Cambridge for example. I did it when was at Leeds in the early 90s.
Despite being a subject reserved for university level, species counterpoint is not actually particularly difficult. If you are around grade 6 theory, it should not be hard. If you know your intervals, you should manage.