Complex sentence: Early success in acquiring reading skills usually leads to later successes in reading as the learner grows, while failing to learn to read before the third or fourth year of schooling may be indicative of life-long problems in learning new skills.
Split into simpler sentences: Early success in acquiring reading skills usually leads to later successes in reading as the learner grows. Failing to learn to read before the third or fourth year of schooling is predictive of life-long problems in learning new skills.