How to get the TaxClassId from an order item?

Question

As described in the title of this question, I don't understand why Magento 1.9.3.0 doesn't save the taxClassId information. Any idea?

$orders = Mage::getModel('sales/order')
            ->getCollection()
            ->addAttributeToSelect('*');

foreach ($orders as $order) {
    $theItems = $order->getAllVisibleItems();
    foreach ($theItems as $product) {
        echo $product->getTaxClassId();
    }   
}

Thanks

Answer 1

You may need to load the product model. E.g.:

$classId = Mage::getModel('catalog/product')
     ->loadByAttribute('sku',$product->getSku())
     ->getTaxClassId();

Answer 2

I know its an old question, but it might benefit who ever is looking for a faster solution that is compatible with Community edition 1.6+

Since taxClassId is a product attribute, you can get the product attribute value without loading the entire product.

$_resource = $this->getProduct()->getResource();

$orders = Mage::getModel('sales/order')
            ->getCollection()
            ->addAttributeToSelect('*');

foreach ($orders as $order) {
    $items = $order->getItemsCollection();
    foreach ($items as $item) {
        $productId = $item->getProductId();
        $taxClassId = $_resource->getAttributeRawValue($_item, 'tax_class_id', Mage::app()->getStore());
        echo $taxClassId;
        echo PHP_EOL;
    }   
}