Siddhattha attained samādhi as a child, and then again under his early teachers. When he was near the night of his Awakening, he recollected the jhana he experienced as a child, and realized that that was the path to Awakening. But why did he reject the experience under his early teachers, even though he reached even higher levels of samādhi, the formless attainments? I can make sense of this only in consideration of the broader context.
When he realized the attainment of jhana as a child his mind was free of theories and control. He was alone under the tree, that is, in the realm of nature. But the event was an ‘accident’. His attainment was part of the intuitive cycle of nature, and as a child he had no way of understanding or reflecting on what had happened.
Under his teachers Āḷāra Kālāma and Udaka Rāmaputta, however, he first learnt the theory, that is, the rational explanation of his mystical experiences. This point is emphasized in the original text, but ignored by most discussions of this point. It was that very theory that prevented these meditations from ripening in full Awakening, presumably because they identified a purified state of consciousness with the Eternal Self. Hence he rejected, not the meditative experiences as such, but ‘that Dhamma’, that is, the religious system which framed the meditative experience within a particular dogmatic framework. He started his practice with wrong view, and hence his samādhi was wrong samādhi: it did not lead to insight.
In each case his experience was unbalanced: the jhana as a child came from naïve playfulness with no understanding of the deeper existential implications; while the experience under his early teachers was dominated by an abstract metaphysic in a patriarchal context.
Now he can return to the same practice on a deeper level of understanding. He developed the stages of jhana, inspired by his childhood experience in nature, but with equanimity, not allowing the pleasure to overpower his mind. He was mature, balanced, possessed of the objectivity that allowed him to reflect on the conditionality and nature of the samādhi experience. This became ‘right samādhi': it lead to liberating understanding.