Complex sentence: In the period of Mr.A.M.Hussain the school was succeeding not only in the curricular activities but also in co-curricular activities and several events of co-curricular activities reached up to national level in his regime.
Split into simpler sentences: In the period Mr.A.M.Hussain the school was succeeding not only in the curricular activities but also in co-curricular activities. Several events of co-curricular activities reached upto national level in his regime.